BULLETIN OF
THE BRITISH MUSEUM
(NATURAL HISTORY)
GEOLOGY
VOL. XVI
1968
TRUSTEES OF
THE BRITISH MUSEUM (NATURAL HISTORY)
LONDON: 1970
DATES OF PUBLICATION OF THE PARTS
No. i. gth February ..... 1968
No. 2. 6th February ..... 1968
No. 3. 2oth February . » . . . 1968
No. 4. igth April . . . . . . 1968
No. 5. i4th June 1968
No. 6. 2nd July 1968
No. 7. 1 3th August ..... 1968
PRINTED IN GREAT BRITAIN
BY ALDEN & MOWBRAY LTD
AT THE ALDEN PRESS, OXFORD
CONTENTS
GEOLOGY VOLUME XVI
No. i. Silicified Brachiopods from the Visean of County Fermanagh (II).
C. H. C. BRUNTON i
No. 2. A Revision of the Foraminiferal genus Austrotrillina Parr. C. G.
ADAMS 71
No. 3. British Neocomian Rhynchonelloid Brachiopods. E. F. OWEN AND
R. G. THURRELL 99
No. 4. The Lower Palaeozoic Brachiopod and Trilobite faunas of Anglesey.
D. E. B. BATES 125
No. 5. The Caudal Skeleton in Lower Liassic Pholidophorid Fishes. C.
PATTERSON 201
No. 6. The Subphylum Calcichordata (Jefferies 1967) Primitive fossil
Chordates with Echinoderm affinities. R. P. S. JEFFERIES 241
No. 7. Palaeoniscoidea-Schuppen aus dem Unterdevon Australiens und
Kanadas und aus dem Mitteldevon Spitzbergens. H.-P. SCHULTZE 341
Index to volume XVI 369
SILICIFIED BRACHIOPODS FROMVEBmt
THE VISEAN OF COUNTY
FERMANAGH (II)
C. H. C. BRUNTON
BULLETIN OF
THE BRITISH MUSEUM (NATURAL HISTORY)
GEOLOGY Vol. 16 No. i
LONDON: 1968
SILICIFIED BRACHIOPODS FROM
THE VISEAN OF COUNTY
FERMANAGH (II)
BY
C. H. C. BRUNTON
Pp. 1-70 ; 9 Plates ; 52 Text-figures
BULLETIN OF
THE BRITISH MUSEUM (NATURAL HISTORY)
GEOLOGY Vol. 16, No. i
LONDON: 1968
THE BULLETIN OF THE BRITISH MUSEUM
(NATURAL HISTORY), instituted in 1949, is
issued in five series corresponding to the Departments
of the Museum, and an Historical series.
Parts will appear at irregular intervals as they become
ready. Volumes will contain about three or four
hundred Pages, and will not necessarily be completed
within one calendar year.
In 1965 a separate supplementary series of longer
papers was instituted, numbered serially for each
Department.
This paper is Vol. 16, No. i of the Geological
(Palaeontological] series. The abbreviated titles of the
periodicals cited follow those of the World List of
Scientific Periodicals.
World List abbreviation :
Butt. Br. Mus. nat. Hist. (Geol.).
Trustees of the British Museum (Natural History) 1968
TRUSTEES OF
THE BRITISH MUSEUM (NATURAL HISTORY)
Issued 9 February, 1968 Price £2 ic
SILICIFIED BRACHIOPODS FROM
I THE VISEAN OF COUNTY
i FERMANAGH (II)
By C. H. C. BRUNTON
MS accepted May gth 1967
CONTENTS
Page
I. INTRODUCTION AND ACKNOWLEDGMENTS ..... 4
II. SYSTEMATIC DESCRIPTIONS ....... 4
Superfamily Craniacea Menke ...... 4
Family Craniidae Menke ....... 4
Crania quadrata (M'Coy) ...... 5
Acanthocrania cf. laevis (Keyes) ..... 7
Philhedra trigonalis (M'Coy) ...... 8
Superfamily Enteletacea Waagen . . . . . . 10
Family Enteletidae Waagen . . . . . . 10
Schizophoria resupinata dorsosinuata Demanet . . n
Family Rhipidomellidae Schuchert . . . . . 17
Rhipidomella michelini (L'Eveilte) . . . . . 17
Superfamily Strophomenacea King . . . . . 21
Family Leptaenidae Hall & Clarke . . . . . 21
Leptagonia analoga (Phillips) ...... 29
Superfamily Davidsoniacea King . . . . . . 31
Family Orthotetidae Waagen . . . . . . 31
Brochocarina wexfordensis (Symth) . . . . . 34
Orthotetinid gen. et sp. indet. ..... 39
Family Schuchertellidae Williams ..... 39
Serratocrista fistulosa, gen. et. sp. n. . . . . . 40
Family Meekellidae Stehli ....... 42
Schellwienella radialis (Phillips) ..... 42
Superfamily Chonetacea Bronn ...... 46
Family Chonetidae Bronn ...... 48
Globosochonetes parseptus gen. et. sp. n. 49
Rugosochonetes silleesi sp. n. . . . . . . 55
Rugosochonetes delicatus sp. n. ..... 62
Rugosochonetes transversalis sp. n. ..... 65
Plicochonetes buchianus (de Koninck) .... 67
III. REFERENCES ......... 68
SYNOPSIS
This paper, the second of a series describing the Vis6an brachiopods from near Derrygonelly
in county Fermanagh, deals with the Inarticulata, Enteletacea, Strophomenacea, David-
soniacea and Chonetacea. Brochocarina and Serratocrista are new Davidsoniacean genera and
Globosochonetes a new chonetid genus; four new species are described. Additional evidence is
presented for the separation of Leptagonia from Leptaena and the relationship of the Chonetacea
to the Productacea is discussed.
GEOL. 1 6, i. i
4 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
I. INTRODUCTION AND ACKNOWLEDGMENTS
THIS study follows that of the Productacea (Brunton 1966) as part of a series dealing
with the brachiopods etched out with acid from Visean limestones at the Sillees river
near Bunnahone Lough, or on the southern shore of the nearby Carrick Lough,
about 2 miles N.W. of Derrygonnelly in county Fermanagh, Northern Ireland. All
the material is from these localities unless otherwise stated in the text, and is of a Low
D zone age. A locality map was given in the previous part (Brunton 1966 ; 178, fig. 2) .
I take pleasure in thanking Professor A. Williams for his help and encouragement
while engaged upon much of the work in his department during the tenure of a
D.S.I. R. studentship. I am grateful to Dr. H. M. Muir-Wood, late of the British
Museum (Natural History); Dr. I. Rolfe, Hunterian Museum, Glasgow; the late
Professor R. G. S. Hudson, Trinity College, Dublin; Dr. G. A. Cooper, Smithsonian
Institution, Washington; Dr. K. E. Caster, University of Cincinnati; Mr. J. M.
Edmonds, University Museum, Oxford and Mr. M. Mitchell, Institute of Geological
Sciences, London for the loan of specimens in their care and for advice. Some of the
photographs were taken by members of the Photographic Department of the British
Museum (Natural History) ; to them and many other helpers I extend my thanks.
I am grateful for having had my attention drawn to the fact that in my previous
publication upon the Productacea (1966) I did not make clear from which locality
new taxa were collected. The information is given below:
Dasyalosia panicula Brunton : Carrick Lough.
D. lamnula Brunton: Bunnahone.
Krotovia lamellosa Brunton: Bunnahone.
Eomarginifera (Eomarginiferina) trispina Brunton: Bunnahone.
II. SYSTEMATIC DESCRIPTIONS
Unless otherwise stated the majority of the specimens here described were collected
from the Sillees River locality (Irish Grid Reference 2105 : 3550) : other specimens are
from the Carrick Lough locality (Irish Grid Reference 2092 : 3538). The fauna
from these localities (separated by a distance of I mile) are considered to be of the
same age (low D Zone).
All specimens prefixed by B or BB are in the collection of the British Museum
(Natural History). The depository of other specimens is given in the text.
Class INARTICULATA
Suborder CRANIIDINA Waagen 1885
Superfamily GRANIACEA Menke 1828
Family CRANIIDAE Menke 1828
Genus CRANIA Retzius 1781
TYPE SPECIES. Anomia craniolaris Linne, by subsequent designation of Schmidt
(1818 : 71).
Williams (1943 : 70) erected the subgenus Lissocrania for " Cranias with dorsal
valves devoid of radial costae or spines. Ornamentation, if any, consists of con-
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 5
centric growth lines or of fine radiating striae or both." The type species, Crania
dodgei Rowley is poorly known and its interior was not described by Rowley (1908),
Weller (1914) or Williams (1943). The type species of Crania s.s., from the Creta-
ceous, and the modern C. anomala (Miiller) are devoid of radial ribbing and may have
slightly larger dorsal posterior adductor scars than anterior scars. Thus, with our
present knowledge, the retention of Lissocrania is unjustified, and in the recently
published Brachiopoda Treatise (1965) it is tentatively placed in synonymy with
Crania.
Other non-ribbed craniid genera are Petrocrania Raymond 1911 (= Craniella
Oehlert 1888) and the poorly known genus Philhedrella Kozlowski 1929, originally
erected as a subgenus of Philedra. Distinction between these two genera may lie
in the presence of well defined dorsal mantle canal traces in Petrocrania and in its
dorsal posterior adductor scars being larger than the anterior scars, apparently
unlike Philhedrella. In his revision of craniids von Huene (1899) included C.
quadrata (M'Coy) and C. kirkbyi Davidson in Craniella (now Petrocrania) , but as this
group is not known to possess sigmoidal mantle canal traces in the dorsal valve they
should probably be removed from Petrocrania. Conceivably they could be assigned
to Philhedrella or Crania. Species at present within Philhedrella range from the
Ordovician to Upper Silurian, while Crania species are described from the Carboni-
ferous times up to the Recent. As the former genus is inadequately known Crania
is perhaps the more appropriate genus within which to place C. quadrata, the species
to which the smooth-shelled Fermanagh craniids are assigned.
There are marked differences in the morphology of Carboniferous and Cretaceous
Crania. The Mesozoic forms are thick shelled with deeply impressed muscle scars,
particularly those of the pedicle valve which are cavernous in form, and a limbus
is common. Palaeozoic shells are thin and the muscle scars are commonly raised
areas in both valves; the brachial valve is without the internal radial ridges seen
between the muscle scars of the Mesozoic forms. Such differences may result from
a greater ability of Mesozoic shells to deposit skeletal material and it may prove more
realistic to distinguish the Palaeozoic species as a group. A clear understanding of
Philhedrella may reveal that this genus would be suitable for some non-ribbed
Palaeozoic species presently assigned to Crania.
Crania quadrata (M'Coy)
(PI. i, figs. 1-9)
1844 Orbicula quadrata M'Coy: 104, pi. 20, fig. i.
1861 Crania quadrata (M'Coy) Davidson: 194, (1863) pi. 48, figs. 1-13.
1899 Craniella quadrata (M'Coy) Huene: 148.
DESCRIPTION. Outline irregular, rounded to subquadrate when undeformed, with
gently folded margin, posteriorly flattened to gently sulcate ; ventral valve entirely
fixed; dorsal valve subconical with beak directed posteriorly and closer to posterior
margin; ornamentation of concentric growth lines and scattered short spine-like
protuberances, valve margins may be slightly thickened; dorsal anterior adductor
6 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
scars close to apex, separated by distance equal to width of scar and from less distinct,
widely spaced posterior scars situated close to valve margin ; slight radial ridge from
beak to valve edge between the muscle scars; shell substance punctate.
MEASUREMENTS (in mm.) :
length width
Incomplete brachial valve (66.55599) c- T^'5 c- 2°'°
Complete brachial valve (66.55600) 7-5 8-6
Complete brachial valve (66.55601) 3-7 3-9
Complete brachial valve (66.55602) 2-2 2-3
Complete brachial valve (66.55603) 2-1 2-4
Incomplete brachial valve (66.55616) 2-1 1-2
DISCUSSION. The fauna from Fermanagh includes a wide range of sizes, from
about i-o mm. to an incomplete brachial valve about 20-0 mm. wide. Pedicle
valves are absent from the collections. Among the juvenile valves are some small
shells of up to 5 mm. long which are almost as high as long and which have well
defined narrow posterior trigonal areas. Together with these highly conical valves
are more typically proportioned specimens looking more like the larger specimens.
It may be that different habitats induced differing juvenile forms or that we have in
the collection a different species, only represented by these small shells. An example
of these conical forms is figured (PI. i, figs. 6, 7). Normally the larger valves are
about one-half as high as long.
Valve outline is variable, depending upon the shell's site of attachment and pro-
bably upon its degree of crowding, but one well formed specimen, with a high
degree of bilateral symmetry may be taken as being typical of undeformed specimens
(PL i, figs. 4, 5). The posterior trigonal area is differentiated by a pair of shallow
sulci extending from the beak to the valve margin. Anteriorly the margin is slightly
bilobed as a result of a third antero-median shallow groove. These features, to-
gether with the more posteriorly placed beak, give the valves a distinct orientation.
Although appearing smooth externally, save for a few growth-lines, these valves are
also ornamented by sparcely scattered more or less concentrically arranged spine-
like protuberances. The possibility that these structures are an artifact of the sili-
cification process has been recognized, but rejected on account of their regular de-
velopment upon the specimens available. Rarely these " spines " can be seen to
project at a high angle from the surface, but only for about o-i mm., and they are
spaced about 0-4 mm. apart. This is considerably more widely scattered than are
the " spines " of Acanthocrania.
Internally the anterior muscle scars are situated towards the top of the trigonal
posterior region, on the slight infolds of the valve, and extend for nearly one-half of
the distance towards the margin. The smaller, more rounded posterior scars are not
radially aligned with the anterior scars and are only slightly more widely spaced.
Dividing the trigonal area is a slight median thickening which is most clearly de-
veloped near the somewhat thickened valve margin.
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 7
In 1858 Davidson erected the species Crania kirkbyi, from the Permian of N.E.
England, which he described as being "... sub-quadrate, with rounded angles, and
is sometimes a little indented at its anterior margin ". Davidson continued by
saying that the external surface was closely covered by a multitude of minute,
short, hollow, spinose tubercles, which produce a granulated aspect." (1858 : 49).
The interior was poorly described. In 1863 Davidson added a note upon the species
saying that he thought the granulation was unnatural and that his species may be
the same as C. quadrata (M'Coy) from the Carboniferous. He figured the two species
on plate 54 (1863) and the two appear identical If Davidson's first impressions
regarding the granulated looking surface of C. kirkbyi were correct it would seem
even more likely that the two are conspecific.
Genus ACANTHOCRANIA Williams 1943
TYPE SPECIES. Crania spiculata Rowley (1908), by original designation of
Williams (1943 : 71).
Acanthocrania cf. laevis (Keyes)
(PI. i, figs. 10-14)
1894 Crania laevis Keyes: 40.
1914 Crania laevis Keyes; Weller: 47, pi. i, fig. 33.
DESCRIPTION. Outline transversely elliptical with flattened posterior margin;
ventral valve unknown; dorsal valve deep, lateral profile asymmetric, anteriorly
evenly convex, posteriorly steep to concave ; beak posteriorly directed and may be
below valve apex; ornamentation of sporadic sublamellose growth-lines and closely
spaced radially directed spines at low angle to valve surface, arranged more or less
concentrically and quincuncially ; adductor scars divided, anterior pair just
posterior of valve apex, near beak, similarly sized posterior scars close to valve
margin and widely separated; shell substance punctate.
MEASUREMENTS (in mm.)
length width
Complete brachial valve (66.55604) 4-6 5-7
DISCUSSION. Wright (1963 : 249) discusses the genus mentioning its range from
the Ordovician to the Carboniferous. The first record of the genus from the British
Isles is that of Wright for Ashgillian specimens from the Portrane Limestone of
Co. Dublin. The type species is a North American Visean form and this Fermanagh
record is the first from the upper Palaeozoic of the British Isles.
The specific description of A . laevis given by Keyes is inadequate and the species
not illustrated. However, Weller (1914) gave a full description, with a figure, of
the specimen from "... the Burlington Limestone . . . used by Keyes ", and from
8 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
this it is clear that it is closely comparable to the Fermanagh material. The specific
name given by Keyes (1894) is inapt but possibly results from the lectotype being
silicified and the papillose surface being thought to result from this process.
Keyes noted that the surface was " marked by concentric lines of growth ", but it
was Weller who described the papillose or spinose nature of the surface. This
external ornamentation is well preserved on the few valves available from Fermanagh
and near the margins, where the " spines " are longest, they are up to 0-4 mm. long.
These papillae or spines may be morphologically associated with the shell punctua-
tion, which is only clearly visible on the internal surfaces of the Fermanagh speci-
mens. The spines arise from the shell in positions corresponding to the internal
positions of punctation and both have similar numbers per unit area, although there
are commonly rather more spines. This may result from the coalescence of several
juvenile punctae into a single larger puncta within younger parts of the shell. This
has been described previously in Crania (e.g. Joubin, Blockman) and recently re-
figured by Rowell (in Williams et al. 1965, fig. 77).
Weller's description (1914 : 48) of the brachial valve interior of the American
material is accurate for the present specimens and the widely spaced posterior
adductor scars are slightly larger than the closely and apically placed anterior scars.
The posterior scars are less well defined and it is likely that with age they would have
grown more prominent and proportionately still larger than the anterior scars. The
margins of the valve are not greatly thickened although slight lamellae were de-
veloped.
As there is only one complete specimen, together with fragments, it is impossible
to present variation studies on this species. Rarely the brachial valve may have
grown in a distorted fashion and may show signs of the skeletal material against
which it grew.
Genus PHILHEDRA Koken 1889
TYPE SPECIES. Philhedra baltica Koken by original designation of Koken (1889 :
465).
Philhedra trigonalis (M'Coy)
(PI. i, figs. 15-29)
1844 Orbiculata trigonalis M'Coy: 401, pi. 20, fig. 2.
1899 Philhedra trigonalis (M'Coy) Huene: 147.
DESCRIPTION. Outline subrounded to longitudinally subelliptical ; profiles asym-
metrical and variable with beak posterior of mid-length and at apex of valve;
margins of brachial valve irregularly shaped through contact with substrate ; growth-
lines distinct and commonly interrupting radial ribs which extend from near apex
to valve margins, ribs increase in width and added by branching and rare intercala-
tion; brachial valve interior with anterior adductor scars slightly raised, oval,
closely placed near beak and divergent towards less distinct ovoid posterior scars
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 9
which extend close to valve margin; pedicle valve thin and poorly known, with
growth-lines and distorted to conform to object of attachment; shell substance
punctate.
MEASUREMENTS (in mm.)
length width
Complete brachial valve (66.55608) n-o 8-4
Incomplete brachial valve (66.55609) 11-4 c. 7-5
Complete shell attached to rugosochonetid
(66.55607) 8-5 7-5
Complete brachial valve (66.55610) 8-0 6-7
Distorted brachial valve (66.55611) 6-9 7-4
Incomplete shell (66.55612) 5-7 5-6
Complete brachial valve ( (66.55613) 4-0 4-2
Complete brachial valve (66.55614) 2-7 2-5
DISCUSSION. The Fermanagh sample is varied in size (having a range of from
2-0 mm. to 12-0 mm. long) and outline. The beak is asymmetrically placed and the
height of the shells differs from just under one-half to less than one-quarter of the
shell length. Ventral valves are rarely preserved and their interiors have not been
observed. However, it is clear that these valves were much effected by the sub-
strate; they commonly show growth-lines and are punctate.
The dorsal valve is rounded to subelliptical in outline with little or no posterior
flattening, as is common in Acanthocrania and Philhedrella. The posterior slope is
less steep than in these genera although the beak is posterior of mid-length. The
larger shells are more elongate than the smaller ones and in profile they retain their
height for a short distance before dropping to the anterior margin (PL i, fig. 17).
The costae arose within about I mm. of the beak and costellae were added by unequal
branching or intercalation. The rib crests are somewhat serrated and commonly
interrupted by the growth-lines; their width increases slightly towards the valve
margins. Some shells became distorted from growth against foreign objects, such
as fenestellid colonies, (PI. i, fig. 25) and the substrate upon which the shells grew
had a marked effect upon the shape of the commissure.
Apart from the adductor scars and punctae the brachial valve interior is devoid of
structures. In the present silicified material the punctae are most clearly developed
and largest close to the valve margins. One valve has a tent-like ridge anterior of
the beak and oblique to the mid-line (PL i, fig. 29). The antero-lateral end of this
ridge appears to be broken and there is nothing to suggest that there was another
ridge on the opposite side of the shell or that damage to the shell resulted in its
formation.
The distinction between Crania and Philhedra rests principally upon the relative
sizes of the muscle scars in the dorsal valve and external ornamentation ; Philhedra
being distinguished as having larger anterior scars than posterior scars and better
defined costellate ribbing.
io SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
Class ARTICULATA
Order ORTHIDA Schuchert & Cooper 1932
Superfamily ENTELETACEA Waagen 1884
Family ENTELETIDAE Waagen 1884
Subfamily SCHIZOPHORIINAE Schuchert & Le Vene 1929
Genus SCHIZOPHORIA King 1850
TYPE SPECIES. Anomites resupinatus Martin 1809, by original designation of
King (1850 : 106).
George & Ponsford (1938 : 228) selected a neotype for S. resupinata (Martin)
and this specimen (BM(NH) 66.2420) was later figured by Bond (1942, pi. 21). The
specimen is large; 55-5 mm. long, 72 mm. wide and 32-5 mm. thick, and as Bond said
" would approach Demanet's variety gigantea " (PI. 2, figs. 1-3). The Fermanagh
shells range in length from i mm. to 13-5 mm. and never display the resupination of
the pedicle valve commonly seen in large specimens, such as the neotype.
In his study of Carboniferous Schizophoria Bond (1942, for 1941) divided the
British and Belgium species into those with coarse ornamentation, i.e. with 3 or 4
ribs per mm. about io mm. from the umbo, and those species with fine ribbing, i.e.
6-9 ribs per mm., io mm. from the umbo. Into the former group he placed 5.
resupinata and its varieties gigantea Demanet, dorsosinuata Demanet, lata Demanet,
pinguis Demanet, rotundata Demanet, and elboltonensis George & Ponsford, (which
are further united by having dental plates at about 70° from one another) together
with the species 5. nuda George & Ponsford, S. hudsoni George and 5. connivens
(Phillips). The type specimen of Phillips' species is lost and his figure (1836,
pi. n, fig. 2) is inconclusive. However, Bond selected a neotype from among
specimens in the Gilbertson Collection in the British Museum (Nat. Hist.) (6.387,
re-registered as 66.54902) which is distinguished from 5. resupinata by its more
globose profile, near sulciplicate anterior commissure, short hinge line, narrowly
divergent dental plates (30°) and small size (16 mm. long) . However, Bond admits
that only one specimen with such a commissure was seen in his study and that its
shape variants grade into some of the more rounded and globular variants of 5.
resupinata. The dental plates are said to be a valid distinction. This being so the
Fermanagh shells can not be attributed to S. connivens as their dental plates diverge
at about 70°, like 5. resupinata s.s.
George & Ponsford (1938) spoke of S. dorsosinuata Demanet as a distinct species
and illustrated sections of three specimens that they attributed to Demanet's
variety. Two of these illustrations (1938, figs. 11, 14) are of interest in that the
brachiophore bases are at an angle to the brachiophores, as are those of the Fer-
managh shells. Serial sectioning has confirmed this feature in a topotype specimen
of Demanet's var. dorsosinuata from Tournai, 6elgium (kindly presented by Dr. P.
Sartenaer) and has led me to assign the Fermanagh specimens to what I consider
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH n
the subspecies 5. resupinata dorsosinuata Demanet. The brachial valve of the neo-
type is sulcate for approximately the first 50 mm. of its length. This dorsal sulcation
is not a common feature but when present most probably produced a unisulcate
anterior commissure, similar to that of the present material, before the onset of
resupination of their pedicle valves.
Schizophoria resupinata (Martin) dorsosinuata Demanet
(PL 2, figs. 7-37; Text-figs. 1-4)
1861 Orthis resupinata (Martin) Davidson (pars.): 130, pi. 30, fig. i, non figs. 2-5.
1934 Schizophoria resupinata var. dorsosinuata Demanet: 53, pi. 3, fig. 14, 15.
1938 Schizophoria cf. dorsosinuata Demanet; George & Pensford, figs n, 14.
1942 Schizophoria resupinata var. dorsosinuata Demanet; Bond: 289.
DIAGNOSIS. Small, biconvex dorsally sulcate Schizophoria with unisulcate
anterior commissure; brachiophores subparallel but brachiophore bases diverging
to valve floor.
DESCRIPTION. Outline rounded subrectangular, length about four-fifths maxi-
mum width, hinge-line straight, about one-half width, cardinal extremities rounded,
anterior margin gently rounded to emarginate and commissure slightly unisulcate;
profile biconvex, depth about one-half length, increasing with age; gentle dorsal
sulcation; radial ornament of low rounded and delicate ribs, about 14 in 2-5 mm.
at 5 mm. antero-medianly from dorsal umbo, about 10 costae and first order costellae
commonly remaining prominent ; branching by intercalation and rib apertures well
developed; concentric ornament sporadic but distinct; ventral interarea concave,
apsacline, delthyrium triangular, open; dorsal interarea about one-half length of
ventral interarea, curved anacline, with open notothyrium, chilidium obsolete; teeth
strong, triangular in outline and diverging at about 45° from mid-line, supported by
receding divergent plates fused posteriorly to inner surfaces of umbonal slopes;
notch below teeth articulating with apophyses on brachiophores; base of dental
plates extending anteriorly as ridges laterally enclosing oval muscle scars about two-
fifths valve length ; muscle field width about three quarters its length and medianly
divided by strong anteriorly widening ridge on antero-lateral faces of which are
narrow lanceolate adductor scars; mantle canal traces obscure, but pair of strong
vascula media extend anteriorly from anterior ends of each diductor scar; cardinal
process developed as ridges across floor of notothyrial cavity, between brachiophore
bases, with distally expanded and incised myophore, trilobed in adults; brachio-
phores strong, diverging at about 40° from mid-line, median faces vertically disposed
and fulcral plates well developed; brachiophore bases diverging to valve floor,
continued anteriorly as indistinct ridges surrounding adductor field but interrupted
by traces of three mantle canals ; adductor field about four-ninths valve length and
about as long as wide, divided medianly and into posterior and anterior scars;
marginal follicular embayments may persist posteriorly.
12 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
MEASUREMENTS (in mm.)
length width
Complete shell (66.52701) 13-8 16-0
Complete shell (66.52702) 13-0
Pedicle valve (66.52703) 11-3 14-5
Incomplete brachial valve (66.52705) 12-5
Complete brachial valve (66.52707) 3-1 3-7
Complete brachial valve (66.52708) 3-8 4-6
Complete brachial valve (66.52709) 5*5 6-7
Incomplete brachial valve (66.52711) c. 16-0
Complete pedicle valve (66.52713) 2-0 2-6
Complete pedicle valve (66.52714) 7-0 8-5
Incomplete brachial valve (66.52715) c. 11-5
Complete shell (66.52716) 2-9 3-6
Complete shell (66.52717) 1-3 1-6
DISCUSSION. The present Fermanagh Schizophoria specimens accord most
closely with Demanet's variety from the Tournaisian of 6elgium. Similar specimens
were described by Sanders (1958 : 43) from rocks of Kinderhook age in Mexico
under the new name 5. sulcata. This silicified material shows interiors comparable
to those from Fermanagh although the Mexican shells are about 10 mm. longer and
relatively thicker. The cardinal process's of both faunas are comparable in having
a bifid central lobe and a pair of lateral lobes within the notothyrial cavity (Sanders
1958, pi. 3, fig. 19, cf. PI. 2, fig. 17). Sanders characterizes his species by " the
sulcus on each valve ", (p. 44) but only that on the dorsal valve is clear from his
figures.
The external radial ornamentation arose from the initial 10 or 12 costae by the
apparent intercalation of costellae, mostly posteriorly. The costae arose within
0-3 mm. of the umbones of each valve. The brachial valve commonly had a median
costa for about the first 3 mm. of growth which subsequently was usually diverted to
one side of the median sulcus. First order costellae were added at about 0-5 mm. and
second order costellae may show at a length of 1-5-2-0 mm. These additions appear
as intercalations, but on close study it is usually possible to determine from which
parent rib the costella had arisen, and in this way it can be seen that there is a
tendency towards median branching across the sulcus and lateral branching on the
dorsal flanks. On pedicle valves lateral branching is more common in a manner
similar to that illustrated by Williams & Wright (1963 : 23). 6iernat (1959 : 61)
records 12 ventral and 13 dorsal costae on 5. striatula from the mid-Devonian of
Poland. These arose at a length of about 0-45 mm. and with a further 0-5 mm. of
growth both first and second order costellae arose. On young specimens a few mm.
long, only the apical tips of the beaks are free of costae and these areas represent the
brephic valves and protegulal nodes. On Fermanagh shells the ribs are low and
rounded and increase in size only slightly towards the anterior margins so that 2, 6,
8, 3 and I specimens have respectively 12, 13, 14, 15 and 16 ribs in 2-5 mm. at a
distance of 5 mm. from the dorsal umbo. Along the costae and primary costellae,
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 13
which commonly remain rather larger than the intervening ribs, rib apertures
(" hollow costellae " of Schuchert & Cooper, 1932 : 143) occur 3 or 4 times per 10 mm.
length. This frequency appears to be less than illustrated by Davidson (1861,
pi. 30, fig. id) or Sanders (1958, pi. 3, fig. 22) but is probably the result of their in-
creased occurrence with age and size of the shell. These apertures have been inter-
preted as small spine bases viz. Davidson (1861 : 130), Dunbar & Condra (1932 : 54
and Cvancara (1958 : 857). Demanet figures what he describes as an external im-
pression of a brachial valve (1934, pi. 3, fig. 13) of 5. resupinata var. rotundata
Demanet showing minute needle-like rods of iron oxide extending away from the
mould into what must have been shell substance. Demanet (1934 : 52) is un-
doubtedly correct in interpreting these minute rods as being infillings of the shell
punctae. There is no clear evidence yet available indicating the significance of the
rib aperatures. If, however, their open nature at the valve margins, prior to second-
ary shell deposition, indicates a functional origin at the mantle margins, it seems
likely that the apertures may have assisted in the sensory apparatus of the shell in a
way comparable to the "sensory" spines described by Rudwick (1965 : 610). The
development of the ventral interior can be traced readily from valves of less than
2 mm. long, by which stage the bilobate muscle field was well developed (PI. 2,
fig. 32). The teeth were not differentiated from the interarea until the valve was
about 6 mm. long, but the dental plates were already strongly formed and fused with
the inner surfaces of the valve posteriorly. Only along their anterior margins did
the dental plates remain discrete from the valve. The ridges enclosing the lateral
margins of the muscle field were developed by this stage, as was the strong median
ridge, but differentiation within the muscle field is impossible to distinguish. In-
deed, it is commonly impossible to see the narrow adductor scars on the median
ridge or the narrow lateral lobes of the diductor scars even on the largest shells
available. The ventral adjuster scars are rounded trigonal markings upon the inner
surfaces of the dental plates.
The coefficients of correlation for all measured parameters are high (see Tables i, 3)
indicating a regular proportional growth. The increased curvature anteriorly of the
brachial valve results in an allometric effect for length relative to width (p < o-oi),
but is not apparent in the sample for other paired parameters. In his studies of
S. resupinata s.l. from the Lower Carboniferous reefal limestones of northern
England, Parkinson (1954) illustrates a possible allometric change in the growth
ratios of plots of thickness against length or width at a shell width of about 20 mm.
As has been pointed out by Veevers (1959), allometry cannot be clearly indicated
without tests of significance having been applied to differing sectors of the growth
axis, and this Parkinson did not do.
The shallow dorsal sulcus became distinguishable in valves about 3 mm. long,
but became prominently developed between 5 and 10 mm. from the umbo and
persisted to the anterior margin. Internally the dorsal muscle field is discernible in
shells about 2 mm. long, as is the small knob-like cardinal process and, rarely, the
two median mantle canal traces. When the valve was about 3 mm. long a small
ridge started to develop on the postero-lateral surfaces of the brachiophores, within
the sockets, which grew anteriorly to form fulcral plates. These were not sufficiently
I4 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
developed to arch the crural pits until the valve was about 5 mm. long. At this stage
the brachiophore tips were about 2 mm. apart, and although the median ridge had
not yet developed between the adductor scars, they were divided into anterior and
posterior scars by a laterally directed pair of mantle canals (PL 2, fig. 30).
The growth of the cardinal process took place from the apex of the notothyrial
chamber as a longitudinally disposed ridge, to the ventral surface of which were
attached the diductor muscles. The ridge was not divided distally into myophore
lobes, as is commonly found in adult dalmanellids, and the muscle bases presumably
extended along its length and onto its flanks. (Text-fig, i). Shell thickening at the
FIGS. 1-4. Illustrations of the ontogeny of the cardinalia of Schizophoria resupinata
dorsosinuata Demanet showing the development of the trilobed cardinal process from the
notothyrial platform ; br, brachiophore ; br.b, brachiophore base ; car.p, cardinal process
(juvenile primary lobe); c.p, crural pit; f.p, fulcral plate (in Fig. 3 the brachiophore tip is
not drawn so as to reveal the fulcral plate) ; n.p, notothyrial platform; r.f.p, rudimen-
tary fulcral plate on juvenile specimen; s, socket.
base of the cardinal process built a notothyrial platform, distinguishable in valves
about 6 mm. long. This platform remained sunk below the dorsal interarea and
even in adult Fermanagh shells was no more than I mm. long. During growth the
diductor muscle bases must have spread laterally onto a pair of ridges (Text-figs.
2, 3) which developed from the notothyrial platform with deeply crenulated crests,
like that of the median cardinal process itself (PI. 2, fig. 20). In valves over 10 mm.
long a variable degree of fusion occurred between these lateral ridges and the main
median myophore so that the antero-ventral face of the cardinal process and noto-
thyrial platform became trilobed with the notothyrium almost filled by the three
myophore ridges (Text-fig. 4). Additional shell deposition antero-laterally on the
median lobe may have resulted in it having become bifid and in its covering the two
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 15
lateral lobes. The adult cardinal process is, therefore, a composite trilobed structure,
as reported by Demanet (1934 : 47), built principally of the median primary lobe,
but accompanied by secondary lateral lobes added during growth.
In discussing the cardinal process of British Avonian Schizophoria George & Pons-
ford (1938 : 233) illustrate serial sections of several specimens and conclude that,
while it is variable in form, the cardinal process commonly consists simply of a median
serrated " node ". Section 40, of 5. nuda George & Ponsford, would be like that of
the Fermanagh specimens if the " accessory processes " flanked the median ridge
rather than both being on one side. It is possible that less widely spaced sections
would have revealed the secondary lateral lobes and the more ridge-like nature of
the cardinal process across the notothyrial floor. A comparison of type material of
5. nuda, preserved as internal moulds in the British Museum (Natural History)
(66.2407-2411), with brachial valve interiors reasonably assigned to 5. resupinata
s.s. (PL 2, figs. 5, 6) shows that the two are probably comparable within the limits of
specific variation. Bond retained 5. nuda principally because of its unusual state of
preservation, but this hardly seems a worthy reason for specific distinction.
In her study of Mid-Devonian orthoids from Poland, 6iernat (1959 : 57) describes
and figures the variation to be seen in the cardinal process of adult Schizophoria
striatula (Schlotheim) . She writes that the cardinal process "may be single or
bifid ", although it would seem from her figures (1959, text-fig. 20, and pi. 9, figs, i, 2)
that the cardinal process of her material probably grew in a similar way to that of the
Fermanagh specimens, viz. the variation being around a basically trilobed structure.
The difference would seem to be one of terminology, for in her discussion of the
ontogeny of the cardinal process, 6iernat describes how " 2 or 3 elevations appear in
the notothyrial cavity on each side of the cardinal process " and continues by
TABLE i
I mm. (var.) = 6-76 (14-613)
w mm. (var.) = 8-42 (22-280)
r = 0-996
a (var.) = 1-235 (o-ooin)
w mm. (var.) = 8-42 (22-280)
x mm. (var.) = 4-79 (8-355)
r = 0-987
a (var.) = 0-612 (0-00089)
I mm. (var.) = 6-76 (14-613)
tE mm. (var.) = 2-01 (1-189)
r = 0-990
a (var.) = 0-285 (0-00015)
T mm. (var.) = 6-76 (14-613)
31 mm. (var.) = 2-72 (2-838)
r = 0-992
a (var.) = 0-441 (0-00028)
cTI mm. (var.) = 2-72 (2-838)
Hi mm. (var.) = 1-95 (0-866)
r = 0-974
a (var.) = 0-552 (0-00142)
TABLE i. Statistics of length (1), maximum width (w), width of hingeline (x), thickness
(th), and length (dl) and width (di) of the diductor muscle scars of 13 pedicle valves of
Schizophoria resupinata dorsosinuata Demanet.
i6
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
TABLE 2
No. of ribs.
12
13
14
15
16
No. of specimens
2
6
8
3
i
TABLE 2. The number of ribs counted in a width of 2-5 mm., 5 mm. antero-medianly
from the umbo of 20 pedicle valves of Schizophoria resupinate dorsosinuata Demanet.
J mm. (var.) = 5-14 (7'398)
w mm. (var.) = 6-42 (11-899)
r = 0-998
loge l_ (var. loge 1) = 1-514 (0-2469)
loge w (var. logew) = 1-552 (0-2791)
re = 0-997
a (var.) = 1-063 (0-00045)
w mm. (var.) = 6-42 (11-899)
x mm. (var.) = 3-01 (2-714)
r = 0-998
a (var.) = 0-478 (0-00006)
s mm. (var.) = 1-18 (0-206)
t mm. (var.) = 1-92 (0-503)
r = 0-963
a (var.) = 1-563 (0-0119)
TABLE 3
I mm. (var.) = 5-14 (7-398)
tE mm. (var.) =1-31 (0-441)
r = 0-926
a (var.) = 0-244 (0-00053)
_T mm. (var.) = 5-14 (7-398)
aH mm. (var.) = 2-31 (1-446)
r = 0-987
a (var.) = 0-442 (0-00034)
ad mm. (var.) = 2-31 (1-446)
v mm. (var.) = 2-18 (0-773)
r = 0-949
a (var.) = 0-731 (0-00213)
I mm. (var.) = 5-14 (7-398)
s mm. (var.) = 1-18 (0-206)
r = 0-976
a (var.) = 0-167 (0-00020)
TABLE 3. Statistics of length (1), maximum width (w), thickness (th), width of hinge-line
(x), length of adductor scars (ad), width of adductor scars (v), length of the extent of the
brachiophores (s) and the width at the brachiophore tips (t) of 17 brachial valves of
Schizophoria resupinata dorsosinuata Demanet.
saying that the adult anterior aspect may be " multifid " while the lateral elevations
became thicker and " together with the cardinal process fill all width of the noto-
thyrial cavity ". It seems, therefore, that she retains the term cardinal process
only for the central " single or bifid " ridge within the notothyrial cavity and looks
upon the lateral " elevations " as being separate structures. She does not indicate
a function other than that of diductor muscle attachment, nor does she differentiate
the " cardinal process " from lateral elevations in text-fig. 20 (1959 : 57) and it would
seem more reasonable to include all outgrowths of the notothyrial platform as con-
stituents of the cardinal process. The intimacy and degree of fusion between the
lateral ridges and the median ridge preclude the possibility that the lateral ridges
bore the dorsal adjuster muscles.
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 17
The internal surfaces of the valves are variably thickened, specimens from Carrick
Lough commonly being thinner than those from Bunnahone. In these thinner
shelled specimens traces of the radial mantle canals are more prominent, being
marked by low bordering ridges, and are represented externally by slightly accen-
tuated radial ribs. A deepening of these canal traces is usually terminated anteriorly
by a rib aperture (PL 2, fig. 37) which only retained a broad connection to the outer
surface while still close to the valve margin. In some young thin-shelled forms up to
7 or 8 mm. long, the traces of each follicular embayment can be followed back to the
muscle field, but more commonly secondary shell obscured these, except over the
last i mm. towards the valve margin. All these traces probably mark the positions
of small mantle canals that led to each setal follicle at the mantle edges.
Accentuated " growth-lines " tend to be more crowded anteriorly, indicating re-
tradations of late growth, and it may be that these specimens were living in con-
ditions marginal to their optimum habitat so never reaching a size more typical for
the species.
Family RHIPIDOMELLIDAE Schuchert 1913
Genus RHIPIDOMELLA Oehlert 1890
TYPE SPECIES. Terebratula michelini L'Eveille, by original designation of Oehlert
(1890 : 39).
Rhipidomella michelini (L'Eveille) 1835
(PL 3, ngs. 1-25, Text- fig. 5)
DIAGNOSIS. Gently dorsibiconvex Rhipidomella with prominent, trifid cardinal
process and well developed posteriorly convex chilidial plates; ventral diductor
scars subrhombiodal in outline, about three-fifths valve length and without strong
postero-laterally enclosing ridges.
DESCRIPTION. Outline subrounded to rounded trigonal, hinge-line about two-
fifths maximum width which is anterior of mid-length, length slightly less than
width, adult anterior margin only gently curved; profile biconvex with depth
slightly less than one-half length ; slight median sulcation of brachial valve and an-
tero-median flattening of pedicale valve; multi-costellate with 9 or 10 ribs in
2-5 mm., 5 mm. antero-medianly from dorsal umbo, costellae added by bifurcation;
growth-lines sporadic and prominent; ventral interarea concave, apsacline, dethy-
rium open with apical angle of about 80°; dorsal interarea shorter, orthocline to
anacline, notothyrium more or less closed by chilidial plates ; teeth strong, diverging
antero-dorsally at about 40° from mid-line, dental plates vertically disposed but
slightly divergent to valve floor ; pedicle callist developed apically, dental plates with
anteriorly directed notches to receive postero- ventral apophyses of brachiophores ;
adductor field small, oval to rectangular and anteriorly raised; diductor scars
variably impressed, adult scars lobate to subflabellate, surrounding adductor scars,
anteriorly ridged and surrounded by slight thickening from bases of dental plates;
valve margins strongly crenulated; cardinal process prominent, distally trifid with
GEOL. 1 6, I. 2
i8 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
median ridge extending beyond lateral ridges, postero-laterally enclosed by chilidial
plates from below which strong brachiophores extend at 35° to 40° from mid-line;
inner faces of brachiophores curved, and bases recurved to floor of valve to enclose
deep sockets; adductor field quadrate to trigonal, extending about one-half valve
length and separated by low wide ridge which may accommodate dorsal adjuster
muscle scars posteriorly, adductor scars possibly divided with more prominent
rounded-quadrate anterior scars.
MEASUREMENTS (in mm.)
length width
Complete shell (33.52718) 10-9 117
Pedicle valve (66.52719) 8-8
Complete pedicle valve (66.52720) 9-2 9-9
Incomplete pedicle valve (66.52721) c. 15-0
Complete brachial valve (66.52722) 7-6 8-5
6rachial valve (66.52723) 7-0 7-3
Complete shell (66.52724) 4-6 5-0
Young pedicle valve (66.52725) 3-4 3-6
Young brachial valve (66.52726) 3-4 3-6
DISCUSSION. Unlike many species of Rhipidomella, which are dorsibiconvex, the
present material is almost equibiconvex. While both valves are approximately
equal in depth, the convexity of the pedicle valve is greatest posteriorly, close to the
umbo, and that of the brachial valve near to its mid-length. These differences are
associated with the anterior flattening of the pedicle valve and the median to antero-
median slight sulcation of the brachial valve ; features which led to a faintly bilobed
body cavity. The form of the valve profile is also associated with the radial orna-
ment. It can be demonstrated that there is a distinct tendency for branching of
costae and costellae to occur downslope, i.e. over the medianly sulcate region of the
brachial valve branching took place more commonly from the median sides ("in-
ternal " of 6ancroft (1928 : 60)), whereas on the flanks, branches commonly arose
laterally ("externally" 6ancroft) (Williams & Wright 1963 122). The relation-
ship between the mantle edge and the shell margins of dalmanellids has been dis-
cussed by Williams & Wright (1963 : 19), and it seems likely that the radial ornament
of such shells is intimately associated with the mantle canal system. The grooves
seen at certain growth stages on some of the follicular eminences, the shell pro-
tuberances between each setal follicle, can be related to external rib branchings.
These grooves soon reached the dimensions of the previously formed follicular em-
bayments and became buried in secondary shell deposits posteriorly, so that it is
only rarely possible to see the positions of the branchings internally. However, ex-
ternally they are commonly clear and probably accurately mark the positions of
canal and follicular proliferations.
The follicular eminences and embayments form a prominent marginal crenula-
tion in rhipidomellids. The use of these crenulations for supra-specific taxonomic
discrimination raises difficulties. Crenulations vary in detail according to both the
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 19
age of the brachiopod and their distance from the margin of the shell. Certainly the
Fermanagh specimens, believed to be conspecific with the type species of Rhipido-
mella, show variation in the cross-section of their crenulations (Text-fig. 5) at different
distances from the margin. It is important, therefore, to define closely any such
variation used as taxonomic criteria.
A comparision of a small collection of R. henryhousensis Amsden, recently placed
in Dalejina by Boucot et al. (1963 : 337), with the Fermanagh specimens shows that
differences in their marginal crenulations exist, but other differences may be noted;
the absence of chilidial plates and more equally branching ribs in the American
species. These differences are, at the best, merely observations, as the American
mid-point
FIG. 5. Three transverse sections parallel to the hinge-line of Rhipidomella michelini
(L'Eveille) showing the anterior internal marginal crenulations. The mid-point of the
shell is indicated on the sections which are 0-4 mm., (a), 0-6 mm.; (b), and 0-8 mm.;
(c) from the anterior edge of the shell.
material at hand appears to be slightly abraded. A more equal rib branching, i.e.
one in which the branching approaches dichotomy, in R. henryhousensis could ex-
plain the more regular grooves on the follicular eminences at the valve margins. This
seems to be fairly persistent throughout ontogeny, whilst in the Fermanagh speci-
mens a closely comparable style of branching was usually restricted to the first few
mm. of growth.
The rib apertures (or hollow ribs) of Rhipidomella are well known and have, been
assumed to be the bases of spinose extensions of the shell (Davidson 1861 : 133,
pi. 30, figs 6, 7). The frequency of these apertures is not constant in R. michelini ,
but is commonly 3 in 5 mm. length of rib. The apertures face anteriorly and away
from the valve surface at a low angle, their openings being hooded by the rib poster-
iorly. Anteriorly the rib is suppressed for a short distance leaving a slight de-
pression. At no time has any sign of spine-like prolongations been seen attached to
the valves, either from the Fermanagh fauna or from specimens from Clattering
Dykes, possibly figured by Davidson (1861, pi. 30, fig. 6). The openings lead
posteriorly along the rib and into the shell substance at a narrow angle. However,
only marginally do they open internally on to the floor of one of the follicular
embayments. Because of the rapid infilling of these embayments by secondary
20
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
shell, the openings do not persist over the internal surfaces and, therefore, could not
have contained living tissue unless connected by thin strands, such as those joining
to the caecae. It is conceivable that the apertures were analogous to the hollow
spines of productoids (also commonly marginal) in providing some sort of sensory
receptors.
In all known aspects other than the prominence of the muscle scars, in particular
the ventral diductor scars, the shells of the Fermanagh fauna agree with the type
species R. michelini (L'Eveille), as described by Demanet (1934 : 37, pi. 2). Al-
though the longest valves reach about 12 mm. the muscle scars are all faintly im-
pressed and it seems clear that differential shell deposition alone was responsible for
the prominence of the scars found in larger specimens of R. michelini.
Campbell (1957 : 51) casts doubt upon the assumption that the dorsal adductor
scars were divided into two pairs in the Lower Carboniferous species. Judging from
the present material and topotypic material from Belgium (PI. 3, fig. 5) his doubts
seem valid, and no posterior scars have been distinguished with certainty. Demanet
(1934 : 39), Dresser (1954 : 22), and Campbell (1957) believe the pedicle callist
(Schuchert & Cooper 1932 : 9) to be the seat of the ventral pedicle adjuster muscles.
However, it is more likely that it developed because of the anterior retreat of the
junction between the pedicle and outer epithelium (Williams 1956 : 255, who termed
it the " pedicle collar "). The umbonal cavity, between the dental plates, probably
accommodated the base of the pedicle, to which were attached adjuster muscles ex-
tending antero-laterally across the cavity floor onto the bases of the dental plates.
The dorsal adjuster muscles probably passed between and anterior to the dorsal
ends of the diductor muscles and were attached posteriorly between the dorso-
median bases of the brachiophores, close to the base of the cardinal process.
TABLE 4
I mm. (var.) = 4-69 (8-340)
w mm. (var.) = 5-01 (8-836)
r = 0-997
a (var.) = 1-029 (0-000213)
wmm. (var.) = 5-01 (8-836)
Ejj mm. (var.) = 1-64 (0-523)
r = 0-941
a (var.) = 0-245 (0'00°45)
I mm. (var.) = 4-69 (8-340)
x mm. (var.) = 2-34 (1-709)
r = 0-995
a (var.) = 0-452 (0-00014)
x mm. (var.) = 2-34 (1-709)
y mm. (var.) = 2-20 (1-488)
r = 0-992
a (var.) = 0-936 (0-00046)
bi mm. (var.) = 0-74 (0-138)
EJ mm. (var.) = 1-64 (0-523)
r = 0-939
a (var.) = 1-947 (0-0298)
TABLE 4. Statistics of length (1), maximum width (w), length to which the adductor scar
extends (x), width of adductor scars (y), and the widths of the brachiophores at their
junctions to the interarea (bi) and at their anterior tips (b%) in 17 brachial valves of
Rhipidomella michelini (L'Eveille).
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
TABLE 5
Delthyrial angle
65°
70°
75°
80°
85°
No. of specimens
i
3
3
8
2
TABLE 5. The total angle of divergence of the teeth and margins of the delthyrium, in 17
pedicle valves of Rhipidomella michelini (L'Eveill6).
TABLE 6
I mm. (var.) = 4-39 (6-200)
w mm. (var.) = 4-70 (6-859)
r = 0-995
a (var.) = 1-052 (0-00031)
I mm. (var.) = 4-39 (6-200)
mm. (var.) = 2-06 (0-915)
r == 0-989
a (var.) = 0-384 (0-00009)
TABLE 6. Statistics of length (1), width (w), and thickness (th) of 20 shells of Rhipidomella
michelini (L'Eveille).
TABLE 7
No. of ribs
8
9
10
No. of specimens
4
7
6
TABLE 7. The number of ribs in a width of 2-5 mm., 5 mm. antero-medianly of either
umbo on Rhipidomella michelini (L' Eveille).
Order STROPHOMENIDA Opik 1934
Superfamily STROPHOMENACEA King 1846
Family LEPTAENIDAE Hall & Clarke 1894
nom transl. Cooper 1956
Subfamily LEPTAENINAE Hall & Clarke 1894
Genus LEPTAGONIA M'Coy 1844
1844 Leptagonia M'Coy: 116 (pars).
1846 Leptaena King: 28 (pars).
1852 Leptaena (Leptagonia) M'Coy: 223 (pars).
1861 Strophomena Davidson: 119 (pars).
1929 Leptagonia Schuchert & LeVene: 74.
1947 Pseudoleptaena Miloradovich : 96.
1952 Leptaenella Sokolskaja: 35, non Leptaenella Fredericks 1917.
1958 Leptagonia M'Coy; Cvancara: 859.
DIAGNOSIS, (emended) Biconvex, strongly geniculate and rugose Leptaenidea;
ventral and dorsal muscle scars situated upon prominent pseudospondylium and
complex muscle platforms respectively.
22 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
DESCRIPTION. Outline irregularly quadrate, profile of adult disc biconvex,
dorsally directed trail variably developed, commonly affected by opposite folding;
rugae regularly and concentrically developed on disc; costae fine, even, rarely
branching dichotomously ; ventral interarea apsacline, delthyrium wide, covered
apically by pseudodeltidium in various stages of resorption, foramen supra-apical,
commonly sealed in adult shells; dorsal interarea short anacline, chili dium large;
teeth strong, widely divergent, crenulated; dental lamellae continuous with sub-
circular pseudospondylium, elevated anteriorly ; lanceolate adductor scars on broad
median ridge; antero-lateral areas of ventral disc rarely raised as low mounds;
cardinal process lobes strongly projecting from beneath chilidium with posteriorly
directed myophores and strongly curved bases defining subcircular hollow; dorsal
adductor field borne on complex platform with elevated subquadrate posterior
scars, highly arched in young valves, flanking raised triangular to rectangular
anterior scars separated posteriorly by low ridge of secondary shell and anteriorly
by deep groove from which median septum extends anteriorly; adult disc enclosed
anteriorly by secondary ridge; mantle canal system pinnate to lemniscate; shell
substance pseudopunctate.
TYPE SPECIES. Producta analoga Phillips by subsequent designation of Schuchert
& LeVene (1929 : 74).
DISCUSSION. The genus Leptagonia was originally established by M'Coy in 1844,
and was later defined by him as including shells with " both valves abruptly bent at
right angles towards the entering " (brachial) " valve and the rostral portion con-
centrically wrinkled" (1852 : 233). This was done in the belief that Leptaena
Dalman was typified by Leptaena transversalis Dalman (now Plectodonta transversalis,
and thereby restricted to plectambonitacean-like shells).
Six species were described by M'Coy and assigned to Leptagonia, the first being
Producta analoga Phillips, a poorly defined species from the Lower Carboniferous of
Bolland, Yorkshire, and Redesdale, Northumberland, but at that time believed to
be closely related to Leptaena depressa J. de C. Sowerby and L. rugosa Dalman from
the Upper Silurian and Upper Ordovician respectively, and also to Productus
plicatilis J. de C. Sowerby (now type species of Plicatifera Chao. from the Carboni-
ferous). In 1855 he included Leptaena distorta J. de C. Sowerby within Leptagonia,
a species also from the Lower Carboniferous.
Davidson (1861 : 119-122) concluded that L. depressa, L. analoga and L. distorta
were synonymous and did not merit more than varietal rank of Strophomena rhom-
boidalis (Wahlemberg) .
In describing Leptaena as a species of Strophomena, Davidson was exercising the
conservatism that pervaded his approach to brachiopod systematics, because King
(1846) had already named a rugate, geniculate species of Dalman, viz. Leptaena
rugosa (see Spjeldnaes 1957 : 172) as type species of Leptaena.
Until recently most palaeontologists have accepted the Carboniferous form as a
true Leptaena, differing only specifically from L. rugosa, L. rhomboidalis , L. depressa,
etc. although Hall & Clarke (1891 : 280) did observe that " the extreme differentia-
tion of the muscular area as described is even more distinctly exhibited in the forms
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 23
of the early Carboniferous than in those of the Silurian and Devonian ". During the
early part of this century L. analoga continued to be thought of as a true Leptaena;
admittedly Schuchert & LeVene (1929) designated the species as the type of Lep-
tagonia, but then promptly described M' Coy's genus as a subjective synonym of
Leptaena.
In 1947, Miloradovich proposed the genus Pseudoleptaena for leptaenids with a
pseudospondylium and a cruralium and cited L. distorta Sowerby as the type; and
in 1952 Sokolskaja erected the genus Leptaenella for leptaenids with a ventral pseudo-
spondylium, naming P. analoga Phillips as type species. In so doing she was evi-
dently unaware that not only had P. analoga been already designated as the type
species of Leptagonia by Schuchert & LeVene, but also that Leptaenella had already
been proposed by Fredericks (1918 : 89) for certain Devonian leptaenids that appear
to be congeneric with Leptaena s.s. Thus, in effect, Russian palaeontologists are
recognising the generic validity of Leptagonia and the problem becomes one of
deciding firstly, if Leptagonia is sufficiently distinct from Leptaena to warrant resusci-
tation; and secondly whether Pseudoleptaena, as typified by L. distorta, is also
different enough to be retained.
Some of the more pertinent features that differentiate Leptagonia from Leptaena
are as follows. In Leptaena geniculation is like an exaggeration of the anterior ruga
so that both valves bend in the same direction, whereas Leptagonia is dominantly
biconvex as a result of valve growth towards the commissural plane, prior to the
strong geniculation. Although the ventral interiors do not greatly differ in general
arrangement, the pseudospondylium of Leptagonia is an expression of anterior
growth of the confining rim of the ventral muscle field away from the floor of the
valve and as such is developed more fully than in Leptaena (PI. 3, fig. 28 ; Text-fig. 7).
Anteriorly it is so elevated as to simulate a true spondylium simplex (Text-fig. 8).
The superficial pattern of the dorsal muscle fields for L. depressa and Leptagonia are
similar, but it originates in different ways. In Leptaena the dorsal adductors were
attached directly to the floor of the brachial valve and were surrounded or slightly
elevated by normal processes of shell accretion during growth of the shell. The
ontogenetic development of the dorsal muscle field of Leptagonia, as seen in a series of
dorsal interiors varying in width from 3-7 mm. to 60 mm., on the other hand, was
intimately connected with two pairs of muscle plates. In the smallest specimens
these plates arise from the floor of the valve, a median pair from below the cardinal
process extending anteriorly and separated by a deep groove ; and a lateral pair arising
from the anterior edges of the socket plates and extending anterolaterally to flank the
median pair. These plates are only fused to the floor of the valve posteriorly and at
their lateral margins (Text-fig. 10) so as to form anteriorly and antero-laterally direc-
ted cavities, all of which must have contained folds of the dorsal mantle epithelium
during early life. Each pair of plates respectively accommodated the bases of the
anterior and posterior adductor muscles. At the same stage of growth, a pair of
ridges extended anteriorly from the points of coalescence of the posterior and anterior
adductor plates with each other and with the floor of the valve, which continue
parallel to the median septum, at a distance of 0-7 mm. on either side of it and for
approximately one-half of its length (PI. 4, fig. 7) ; they are thought to have defined
24 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
the vascula myaria which probably continued posteriorly along the depression
between the anterior and posterior adductor plates. It is also possible that the body
wall, separating the visceral and brachial cavities, may have been supported at these
ridges.
In brachial valves with the median septum extending anteriorly for a distance of
about 9 mm., a considerable amount of shell thickening has taken place. The lobes
of the cardinal process had grown ventrally and are separated distally by a notch of
variable dimension, containing the median indentation of the chilidium. The
rounded pit below the cardinal process is encased in secondary shell obliterating the
posterior ends of the adductor plates. (Text-fig, n). These progressively lost
1mm.
1mm
8
FIGS. 6-8. Illustrations of transverse sections of Leptagonia analoga (Phillips) at 2-0 mm.,
Fig. 6; 3-0 mm., Fig. 7; and 4.5 mm., Fig. 8. from the ventral umbo of a specimen
about 30 mm. wide across the visceral disc, a.a.p, anterior adductor platform; a.r, ad-
ductor ridge in pedicle valve; c, cavity below dorsal adductor platform; c.p, cardinal
process; p.a.p, posterior adductor platform; p.f, pedicle foramen; pss, pseudospondy-
lium.
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
their tent-like shape through infilling of the underlying chambers ; presumably dur-
ing the anterior withdrawal of the mantle epithelium and through secondary shell
deposition by the epithelium associated with the muscle bases. Concurrently, the
ridges lateral to the median septum became increasingly prominent and thickening
10
FIGS. 9-14. Illustrations of the ontogeny of the brachial valve interior of Leptagonia
analoga (Phillips) (Figs. 9-13), and details of the adult cardinal process (Fig. 14). All
viewed dorsally except fig. 10, viewed postero-dorsally. ar, " alveolus ", the subcircular
hollow between the bases of the cardinal process; ch, chilidium; c.p, cardinal process;
m.c, traces of the mantle canals; s.p, socket plates; sr.r, ridge surrounding the sub-
rhomboidal region.
26 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
occurred between them and the anterior part of the median septum to produce a
subrhomboidal structure enclosing the septum anterior to the adductor plates
(cf. Leptaena rhomboidalis] . From the lateral corners of this area small subsidiary
ridges extend forward which probably denned the outer edges of the vascula my aria
trunks. At this stage, the lateral and anterior borders of the adductor plates remain
discrete from the valve floor, but the degree of arching seldom exceeds i mm. In
specimens whose median septum extends n mm. from the base of the cardinal
process, the posterior adductor plates are generally raised above those associated with
the anterior adductor scars (Text-fig. 12). However, this is a temporary feature, as
large specimens, with a median septum of 16-5 mm. have both adductor scars at
much the same level.
In the largest specimens, the infilling of the chambers below the adductor plates
is almost complete, only the lateral margins of the posterior plates showing slight
arching. The anterior and posterior scars are less well differentiated, only being
separated by a low ridge (Text-fig. 13). The posterior and median borders of the
muscle fields are well defined by the continued deposition of secondary shell so as to
form a short median ridge extending from the pit between the cradinal process lobes
and termininating in the groove between the anterior scars. The subrhomboidal
area is well developed and the shell especially thickened round the anterior region of
the median septum. The small subsidiary ridges, marking the vascula myaria can
now be traced anteriorly to where they branch towards the anterior margin of the
brachial cavity. By this stage the cardinal process lobes are well separated ventrally
and their flat ends are slightly striated for the reception of the dorsal diductor bases.
The chilidium had grown ventrally to enclose the posterior faces of the lobes in such
a way as to form two cavities from which the diductor muscles extended (Text-fig.
14).
The point of articulation of the valves was always anterior to the interareas, so
that during growth the chilidium extended antero-laterally to infill the redundant
posterior regions of the sockets. This complicated development contrasts strongly
with the simple accretionary processes that were responsible for the differentiation
of the dorsal adductor scars of Leptaena.
From a provisional investigation of Devonian Leptaena in collections from
Germany and North America it would seem that internal morphology is intermediate
between Silurian Leptaena and Carboniferous Leptagonia. The Devonian muscle
fields are more elevated, especially anteriorly, than those of Silurian specimens, and
the cardinal process, with its supporting ridges is comparable to Leptagonia in that
the myophore bases diverge antero-ventrally to enclose a deep rounded alveolus.
The socket ridges are characteristic in Leptagonia as they curve smoothly onto the
cardinal process rather than being sharply distinct as in L. depressa and L. rhom-
boidalis.
In his original description of L. distorta, the type species of Pseudoleptaena,
J. de C. Sowerby (1840 : 10) referred to it as having " A thicker shell than L. analoga;
well distinguished by its projecting beak, very convex valves, which are not com-
pressed near the beak, and its smaller size." The specimens were collected by
Gilbertson from the Isle of Man. This description would be adequate for shells at a
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 27
stage of development as illustrated in Text-figs. II and 12, which are essentially
the same as text-fig. 27 of Pseudoleptaena distorta in Sarycheva & Sokolskaja
(1952 : 37). Thus, the cruralium and pseudospondylium of Miloradovich's genus
are developmental stages in the growth of the adult Leptagonia and invalidate the
retention of Pseudoleptaena as a distinct genus.
The mantle canal system of Leptagonia differs somewhat from that illustrated for
Leptaena by Williams (1956 : 274). His illustration shows saccate gonocoels sur-
rounded by major sinus trunks from which are given off numerous peripheral sinuses.
In Leptagonia it appears that the gonocoels themselves were lemniscate, giving off
the periferal sinuses (PI. 3, fig. 30), with the vascula media and my aria retained
medianly (Text-fig. 15). However, it might be that this condition is only apparent,
and could have developed from the pattern illustrated by Williams by the enlarge-
ment of the gonocoels so as to have ruptured some of the more peripheral mantle
sinuses and their main connecting trunks. Fragments of traces of the mantle
1 cm.
FIG. 15. Illustration of an internal mould of the pedicle valve of Leptagonia analoga
(Phillips), showing the impressions of the pseudospondylium and mantle canals; a.s,
scars of adductor muscles; d.s, scar of diductor muscles; g, gonocoel, with traces of
peripheral canals; v.m, vasculum medium canal traces.
canals can be seen throughout most of the thickness of the shell substance and always
seem to arise from the edges of the gonocoel, rather than from main vascula trunks,
so that it seems unlikely that overgrowth of the gonadial regions has oblitered a
former pattern of the mantle canal system. Cvancara (1958 : 861) speaks of " two
suboval areas " on either side of the dorsal and ventral muscle fields which he says
" appear " to be the only areas of pseudopunctation in Leptagonia. It seems likely
that the regions to which he refers are the finely papillose areas, here considered as
gonocoels (PI. 4, fig. 2) and that he is incorrect in thinking the teleolae to be confined
to those regions. Admittedly, there is a concentration of taleolae in the shell
substance antero-lateral of the muscle fields, but they also occur within the shell
substance of the muscle platforms and are scattered throughout the rest of the
shell. From internal moulds it seems probable that the taleolae were also concen-
trated more strongly at the base of the trail. The pseudopunctae of Leptagonia
are inwardly directed flexures of the shell fibres surrounding narrow non-fibrous
taleolae so as to produce a closely fitting series of sharp cones, marked internally
28 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
by small tubercles. They were probably formed at the points of attachment of
small muscle strands within the mantle, which may have assisted in the circulation
or explusion of the gonadial products from the mantle canal system, and in the
movement of the mantle edges. Such an interpretation might explain the concentra-
tion of taleolae in the gonadial regions, and at the base of the trail.
An unusual feature seen rarely in pedicle valves is the development of two slight
conical thickenings of the shell symmetrically placed between the pseudospondylium
and the anterior margin of the disc. Similar, though more papillose humps are to
be seen in some Silurian leptaenids, and may indicate that the spirolophe was slightly
conical and directed towards the dorsal valve.
Longitudinal sections of young shells, of hinge-width approximately 2-5 cm.
show an open supra-apical pedicle foramen. A study of the shell texture shows the
canal through the shell to be lined with fibres disposed parallel to the canal surface
and more or less normal to the ventral, external, surface of the valve, an area which
FIG. 1 6. Illustration of a median longitudinal section through a young shell of Leptagonia
analoga (Phillips) showing the cavity below the dorsal adductor platform, thickening
anterior to the cardinal process and the pedicle aperture with its lining of secondary
fibrous calcite; a.p, adductor platform; c.p, cardinal process; p.a, pedicle aperture.
must have been covered by chitin (Text-fig. 16). In describing his Australian
specimens of cf. L. analoga Cvancara (1958 : 860) apparently noted the same feature
for he states that " The foramen appears to be lined with a tubular sheath ". The
disposition of these fibres and their inferred relationship to the epithelium which
secreted them is obscure, but it would seem likely that they were deposited during the
withdrawal of the outer epithelium following the development and redundancy of the
nepionic pedicle sheath (Arber 1939 : 84). Outer epithelium must have extended
through the nepionic shell to have formed the pedicle sheath. During subsequent
growth the withdrawal of the outer epithelium resulted in the deposition of fibres
parallel to the pedicle canal and also drew its junction with the pedicle epithelium
inwards, so lining the canal with chitin. Spaces within the shell substance, parallel
to these fibres, suggest that there might have been periodic advance and retraction
of the outer epithelium to pedicle epithelium boundary.
In 1958 Cvancara came to the same conclusions about the reintroduction of
Leptagonia as the correct generic name for the distinctive Carboniferous leptaenids.
He bases his reasoning upon a study of the ventral valves in which he observed the
muscle field to be supported upon a " well-developed spondylium ", in contrast to
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 29
the flat muscle field of Leptaena. Cvancara did not examine the type specimen of
L. analoga, but there can be little doubt that the upper Tournasian specimens from
New South Wales which he describes are closely comparable with Phillips' species.
Leptagonia analoga (Phillips)
(PL 3, figs. 26-31. PL 4, figs. 1-9. Text-figs. 6-17)
1836 Producta analoga Phillips: 116, pi. 7, fig. 10.
1844 Leptagonia analoga (Phillips) M'Coy: 117.
1861 Strophomena rhomboidalis var. analoga (Phillips) Davidson: 119, pi. 28, figs. 1-6, 9-13.
1958 Leptagonia cf. L. analoga (Phillips); Cvancara: 860, pi. 100, figs 6-13.
DIAGNOSIS. Subquadrate to semicircular Leptagonia with adult disc about one-
half as long as wide, outline commonly modified by emargination medianly and less
commonly laterally; immature shells plano-convex, adult shells biconvex, about one-
half as deep as long, commonly uniplicate, rarely parasulcate ; dorsally directed trail
variably developed; visceral region with 14-18 regular rugae having mean wave-
lengths of i-o mm. and 1-4 mm. for the fifth and tenth rugae; rounded costae,
commonly 5 or 6 in 2 mm., 10 mm. antero-medianly of umbones; pseudospondylium
subcircular, seven-tenths as long as wide and about one-third as long as length of
disc; dorsal muscle field one-half as long as wide, median septum extending forward
for about two-fifths length of disc.
MEASUREMENTS (in mm.)
length width
LECTOTYPE. Complete eroded specimen (6.8963) c. 20 c. 44
Incomplete pedicle valve (L. 3817/1) 32 c. 50
Incomplete brachial valve (68.52731) c. 54
Complete brachial valve (66.52730) 6-0 c. 6-9
Internal mould (66.55777) 3° c- 45
Complete shell (66.52729) c. 5-0 5-5
LOCALITIES AND HORIZONS: Lectotype from 6olland, Yorkshire. 6.8936
(PL 3, figs. 26, 27).
L. 3817/1 from the Caldwell Collection, Hunterian Museum, Glasgow, collected
from the Lower Carboniferous of Carrick-on-Shannon, Counties Leitrim and Ros-
common, Ireland.
B6.55777 Gilbertson Collection, probably from the Lower Carboniferous of the
Isle of Man.
66.52729-30. The subreefal limestones and shales of 6unnahone, 2 miles N.W.
of Derrygonnelly, Co. Fermanagh. Low. D. zone.
6.. 52731. The 6allyshannon limestone of Streadagh Point, Co. Sligo, Ireland
S2.
DISCUSSION. There is considerable variation of outline and in the length of
visceral disc at which geniculation took place, so that the number of rugae on the
30 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
ventral discs of nineteen specimens from Carrick-on-Shannon ranges from 13 to 23.
The wave-lengths of the fifth and tenth rugae from the umbo varies from 0-8 mm.
to i-i mm. (mean i-o mm.) and from i-i mm. to i-6mm. (mean 1-4 mm.), on 15
specimens. Costation was little affected by the point at which geniculation occurred
and remains with 3, 6, 4 and 3 specimens having respectively 4, 5, 6 and 7 costae per
2 mm. width at 10 mm. antero-medianly from the ventral umbo. Almost invariably
FIG. 17. Illustration of the anterior region of a median longitudinal section through the
shell of Leptagonia analoga (Phillips) showing the secondary marginal ridge around the
visceral region of the brachial valve, developed at the point of geniculation. The brachial
cavity is to the right on the illustration.
the trail is depressed medianly, commonly also affecting the anterior margin of the
disc to form a uniplicate commissure. Those shells which geniculated before the
more usual disc length of about 27 mm. may be slightly depressed laterally as well as
antero-medianly (cf. Davidson 1861, pi. 28, fig. 7). Such shells have been separated
as L. distorta, but within large samples no satisfactory separation from L. analoga
can be established. All contain the same internal structures at various stages of
development, and the length at which the trail developed ranges from typical
L. distorta, about 15 mm. long, to full sized specimens of L. analoga. It is necessary
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 31
to discover whether valid stratigraphic or fades differences occur within these forms
before being at all sure of their taxonomic positions.
Irregularly concentric fine growth lines are continued on the trail, while the
traces of the mantle canal system can also commonly be seen within the shell sub-
stance below every second or third rib. The rugae are not continued on to the trail.
The ridge around the adult dorsal visceral disc is of secondary shell material and
becomes increasingly prominent through adulthood. (Text-fig. 17).
Only a few specimens of L. analoga were found among the etched material from
Co. Fermanagh, but the author has made use of specimens in the Caldwell Collection
from Carrick-on-Shannon, about 36 miles S.S.W. of Derrygonnelly, kindly lent by
the Hunterian Museum, Glasgow. Measurements on 10 brachial valve interiors
from this collection shows that the length of the median septum, measured from the
posterior margin of the adductor field, is consistently similar to the total width of the
socket ridges (r = 0-924).
Superfamily DAVIDSONIAGEA King 1850
Family ORTHOTETIDAE Waagen 1884
Subfamily ORTHOTETINAE Waagen 1884
' [= Derbyoidinae Thomas 1958]
Genus BROCHOCARINA nov.
1855 Leptaena (Strophomena) M'Coy: 450 (pars).
1861 Streptorhynchus King 1850: Davidson: 123 (pars) pi. 26, figs. 5 (?2 and 6) non Figs, i,
3 and 4.
1910 Schuchertella Girty 1904; Thomas: 126.
1930 Schuchertella Smyth: 555, pi. 15, figs. 5-9.
DIAGNOSIS. Thin plano-convex Orthotitinae with entire chilidium; dental
ridges deep, fusing posteriorly in ventral apex with trifid ridges enclosing lanceolate
adductor scars.
DESCRIPTION. Outline subsemicircular, profile more or less plano-convex with
narrow body cavity; ventral interarea long, apsacline, with arched pseudodeltidium,
perideltidium variably defined; dorsal interarea and chilidium reduced; radial
ornament parvicostellate with costellae regularly intercalated; teeth strong, con-
tinued at delthyrial margins as obliquely disposed posteriorly prominent dental
ridges; ventral muscle field defined only in adult shells, adductor scars lanceolate,
inserted posteriorly between low trifid ridges, diductor scars flanking and spreading
anteriorly ; cardinal process low, lobes well separated by sulcus with median chilidial
ridge; socket plates at about 20° to hinge-line, slightly recurved; adductor field
obscurely impressed, apparently flabellate to subcircular and separated by slight
median ridge in adult shells ; shell substance irregularly pseudopunctate.
TYPE SPECIES. Schuchertella wexfordensis Smyth 1930.
DISCUSSION. The new genus Brochocarina conforms to the requirements of the
family Orthotetidae Waagen 1884, in having a low cardinal process and ventral
32 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
interior with a low median septum continuous with the inside of the pseudodeltidium
and fused to the dental ridges. At subfamilial level the distinction between Ortho-
tetinae Waagen, and Derbyiinae Stehli, is based upon the form of the socket plates;
those genera with widely divergent socket plates, which tend to recurve towards the
posterior margin as they fuse to the dorsal valve floor, being placed in the Ortho-
tetinae, while those genera with less widely divergent socket plates, fusing to the
floor without curvature, being assigned to the Derbyiinae. The genus possesses
somewhat recurved socket plates, an ill-defined dorsal adductor field, greatly re-
duced dorsal interarea and small chilidium and is therefore assigned to the Ortho-
tetinae.
The genera comprising the Orthotetinae are distinguished by differences in their
ventral interiors, the form of the cardinal process lobes and the shell profile. Bro-
chocarina differs from Orthotetes Fischer de Waldheim (? Werriea Campbell 1957)
in having a less highly developed ventral median septum which has never been ob-
served to have fused with the dental ridges posteriorly to such an extent as to have
formed a delthyrial chamber (The " spondylium " of early authors and " secondary
spondylium " of Thomas 1958 : 9). Hipparionyx Vanuxem is clearly distinguished
by its subcircular outline, strongly impressed ventral interior and high, strongly
divergent cardinal process lobes.
A comparison of the original descriptions of Derbyoides Dunbar & Condra (1932 :
114) and Tapajotia Dresser (1954 : 33) suggests that these genera are less distinctive
than was thought by Thomas (1958 : 21) or by Dresser himself. While admitting
" that Tapajotia is closely related to Derbyoides " Dresser separates the two largely
on his mistaken belief that Derbyoides possesses a strong ventral median septum.
In fact Dunbar & Condra (1932 : 115) state that " A median septum is present but
rather weak and low, extending not over one-third the distance to the front of the
valve ", and inspection of their pi. 9, fig. 13 confirms this statement. For the above
reasons Campbell (1957 : 46) states that Tapajotia " is probably a synonym of
Derbyoides ". This conclusion was arrived at by Mendes (1958 : 317, 319) in his re-
view of the Tapajos River fauna of the Amazon Valley, and is supported by Cooper
(personal communication). However, having studied topotypic material of Derby-
oides and Tapajotia the writer is of the opinion that the two genera are distinctive and
worthy of separation from Brochocarina gen. nov., while all three were probably
closely related and derived from a schuchertellid stock.
The distinction between Derbyoides (PI. 4, figs. 10-14) and Tapajotia (PI. 4, figs.
15-23) include the following features. The brachial valve of Derbyoides is " strongly
and rather evenly convex, with the highest point near the mid-length ", (Dunbar &
Condra 1932 : 115) and the valves are commonly faintly medianly sulcate in con-
trast to the plane, posteriorly flattened valves of both Tapajotia and Brochocarina.
Dresser is mistaken in describing the widest part of Tapajotia as being " anterior "
to the transverse mid-line. His illustrations, and the material at hand, show the
greatest width to be at one-third the shell length, and the hinge-line width to be
nine-tenths of this width. The greatest width of Derbyoides is at mid-length and
the hinge-line is only three-quarters this width. The dorsal interiors differ in that
a short median septum is developed between and anterior to the clearly impressed
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
33
adductor scars of Derby oides, neither of which are seen in Tapajotia, and its cardinalia
are more massive, extending for one-third of the hinge-line width as compared to
one-quarter the width in Tapajotia. The ventral adductor scars are similar, but
differ in being more elongately lozenge-shaped in Derby oides, those of Tapajotia
having more or less parallel lateral margins bordered by slight ridges. The delthyrial
angle is about 20° greater in Derby oides than in Tapajotia or Brochocarina, and its shell
substance is much thicker and led to the development of marginal ridges around the
edges of both valves.
FIGS. 18-20. Illustrations comparing the cardinalia of Derby oides Dunbar & Condra
(Fig. 18), Tapajotia Dresser (Fig. 19), and Brochocarina gen. n. (Fig. 20) in posterior
(on the left) and internal (on the right) views.
Brochocarina is distinguished from both Derbyoides and Tapajotia primarily by
reason of its ventral interior. The teeth of the American genera are traced along the
edges of the delthyrium as low ridges which do not fuse at the beak of the valve to
form a ventral median septum. The teeth of Brochocarina are supported by distinct
dental ridges, strongly differentiated from the inner surface of the interarea. In
adulthood these ridges reached almost to the valve floor and throughout life they
fused posteriorly and gave rise to the tripartite median septum that separated and
enclosed the lanceolate adductor scars (pi. 5, figs. 8, 13).
The dorsal cardinalia is similar to that of Tapajotia, but differs in that the socket
plates diverge at 20° to 25° from the hinge-line instead of at about 35° in the Brazilian
and Nebraskan genera (Text-figs. 18-20). The outline of Brochocarina tends to be
more semicircular than that of the other genera, as its maximum width is commonly
GEOL. 1 6, I 3
34 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
at the hinge-line. The plano-convex profile is like that of Tapajotia but different
from the dorsi-biconvex profile of Derbyoides. The external radial ornament, with
about ii ribs in 5 mm. at 10 mm. antero-medianly of the dorsal umbo, is of much the
same frequency as that of the American genera. However, the form of the ribbing
does vary. Brochocarina is parvicostellate with narrow, rather angular ribs which
only attain their full dimensions after about 5 mm. (First order costellae attain full
size after 3 or 4 mm. while second and third order costellae only attain full size after
about 10 mm., if at all.) This led to the development of relatively wide inter-
spaces, especially posteriorly, and this contrasts with the more regular, rounded
radial ornament of the other two genera.
Thus, Brochocarina may be distinguished principally by its ventral interior and
narrowly divergent socket plates. Derbyoides differs in its convex and heavily
thickened brachial valve and in having a medianly developed dorsal septum. The
Fermanagh shells are older than the other genera of the subfamily, except for
Hipparionyx, and yet show a stage of development of the ventral interior apparently
intermediate to that of Tapajotia and Orthotetes. Of the presently described genera
Brochocarina could have been ancestral to Derbyoides and Tapajotia by the reduction
of the dental ridges in these later genera, and to Orthotetes by the increased deposition
of secondary shell in this region.
Brochocarina wexfordensis (Smyth)
(PL 4, figs. 24-26, PL 5, figs. 1-23. Text-figs. 18-26)
1855 ILeptaena (Stromphomena) crenistria (Phillips); M'Coy: 450.
1861 Streptorhynchus crenistria (Phillips) Davidson (pars) : 124, pi. 26, fig. 5, (?2 and 6)
non figs, i, 3 and 4.
1930 Schuchertella wexfordensis Smyth: 555, pi. 20, figs. 5-9.
1931 Derbyia ambigua Muir-Wood (pars) : 144, fig. 3, non pi. 10, figs. 4, 5.
DIAGNOSIS (emended). Outline subsemicircular, with length about two- thirds
maximum width; radial ornament unequi-parvicostellate with about 6 ribs in
2-5 mm. width, 5 mm. antero-medianly from dorsal umbo, interrupted by occasional
growth lamellae, growth-lines numerous; pseudodeltidium arched with apical angle
about 65°, flanked by wide perideltidium with apical angle about 130°, teeth pro-
minent, adult dental ridges deep, almost reaching floor of valve; socket plates low,
about one-quarter hinge width, recurving posteriorly to floor of valve.
MEASUREMENTS (in mm.) :
length width
HOLOTYPE. Complete brachial valve (T.C.D.i96/io86) 36-3 c. 49-6
PARATYPE. Incomplete pedicle valve (T.C.D. 199/1086) 63-5
Incomplete pedicle valve (66.52732) 67-9
Incomplete pedicle valve (66.52734) c. ii-o
Incomplete brachial valve (66.52735) c. 9-5
Complete brachial valve (66.52736) 32-3 c. 53-0
Complete crushed shell (66.52738) c. 64-0 c. 90-0
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 35
LOCALITIES AND HORIZONS: Holotype and paratype: Smyth Collection
Nos. 196/1086, 199/1086 at Trinity College, Dublin, collected from Lower Carboni-
ferous rocks on the west side of Hook Head, Co. Wexford. ?Ci.
66.52732-52736 : Subreefal limestones and shales of Bunnahone and Carrick Loughs,
2 miles N.W. of Derrygonnelly, Co. Fermanagh. Dx. 66.52738: Bundoran
shales, Bundoran, Co. Donegal. S2.
DISCUSSION. In all known respects the present Fermanagh material agrees with
the type specimens of Schuchertella wexfordensis Smyth, 1930, from upper Tournaisian
and lower Visean beds of Hook Head, Co. Wexford. Although a statistical com-
parison of the growth axes " a " for the Hook Head and Fermanagh specimens in-
dicates that there is a slight significant difference (0-02 < p < 0-05), the ventral
interiors are identical (cf. PI. 4, fig. 24 with PI. 5, fig. 13) and no differences can be
distinguished between the external ornamentation. The two are, therefore, con-
sidered to be conspecific.
In 1931 Muir-Wood (in Garwood) described a new species of davidsoniacean,
Derbyia ambigua, from C2 beds in Roxburghshire. Five of the original specimens are
in the British Museum (Nat. Hist.), but they are not all conspecific and two (6.56425,
6.56410) are thought to be conspecific with Smyth's species while a third fragment
(6.56415) is probably conspecific. The holotype of D. ambigu (6.56411) and the
pedicle valve interior (6.56416) figured (1931, pi. 10, fig. 5) are distinctive. Without
brachial valve interiors it is difficult to be certain about the generic designation, but
the high ventral median septum and small delthyrial cavity are more reminiscent of
Orthotetes than Derbyia.
The description of Leptaena (Strophomena) crenistria (Phillips), given by M'Coy
in 1855 (: 450) is in agreement with the present species in all recorded features.
However, it is not conspecific with Spirifera crenistria Phillips (1836 : 216) which has
a convex brachial valve (pi. 9, fig. 6) and is assigned correctly by Thomas to Schellwie-
nella (1910 : 126). The illustration of Streptorhynchus crenistria (Phillips) by David-
son (1861, pi. 26, fig. 5) has been variously ascribed; to Schuchertella by Thomas
(1910) and Smyth (1930 : 555), and to Tapajotia by Dresser (1954 : 37). Dresser
considered Davidson's specimens to be " specifically distinct from T. tapajotensis
because they possess a much deeper impression of the muscle scars in both valves ".
This observation could be used to separate the present species from that illustrated by
Davidson. It should be remembered, however, that his specimen illustrated in
fig. 5 is from Hook Head, the type locality, and that several of Davidson's illustrations
are somewhat stylized. It may be that Davidson's figs. 2 and 6 (cf. pi. 26) are also
conspecific.
The species differs from Schuchertella pseudoseptata Campbell (1957 ' 46), des-
cribed by him as closely resembling 5. wexfordensis, by not having socket plates which
are parallel to the hinge-line. Campbell's species apparently never reached the
dimensions of S. wexfordensis, and from the description is only comparable in its
ventral muscle field and septation.
Growth of the shell was almost equally radial to give a high coefficient of correla-
tion between length and width (r = 0-998). The greatest width is almost invariably
at the hinge-line, so that the cardinal extremities remain at 90° or less. Costellation
36 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
is probably a reflection of setal growth at the mantle margin, and as such remains
constant throughout several genera of the davidsoniaceans. As in other genera, the
costae number sixteen to eighteen on each valve, one to four orders of costellae being
regularly and symmetrically intercalated so that in a width of 2-5 mm. antero-
medianly of the dorsal umbo the costellae are arranged as in Table 8. Because of the
flatness of these shells, and the frequency with which their anterior margins are
broken, the best estimate of shell thickness is gained by measuring the height of
the delthyrium (Table n). From the complete specimens available it is clear that
this posterior region represents the region of greatest shell depth.
Fine growth lines form minute ridges across the crests of the costellae which
became increasingly prominent anteriorly, until in adult shells, the ridges are pro-
longed into small spinose lamellae PI. 5, fig. 12. Concentric lamellae, formed by
interruptions in growth, are variably developed, although they tend to be concen-
trated towards the adult shell margins, presumably because of reduced shell growth.
An unusual characteristic of the species, is the way in which the brachial valve
commonly becomes flat, or slightly concave, over a distance of about 10 mm.
immediately anterior to the initial convexity of the umbonal region. The peridel-
tidium, which is best seen on calcareous shells (PI. 5, fig. 19), extends laterally for
about one-half the width of the ventral interarea and is finely striated vertically,
as well as bearing the sporadic growth lines that traverse the whole interarea and
pseudodeltidium. It is possible that a similar area occurs upon the dorsal interarea.
Clearly the periostracal shell covering was differentiated in the perideltidial region
and the fine vertical striations are suggestive of a tight bonding to the shell surface,
as might be expected under a periostracal pad (Williams 1956 : 257).
The chilidium is best seen in adult shells, (PI. 5, figs. 6, 18) but its development can
be followed from shells only about 3 mm. wide. In adult shells, with a dorsal in-
terarea 1-5 mm. long, the chilidium curves around the base of the cardinal process
lobes and is separated from them laterally by prominent grooves. A short chilidial
ridge supports the structure between the cardinal process lobes and laterally it merges
with the socket plates.
Internally, the margins of adult shells are commonly secondarily thickened to a
greater extent than the remaining surfaces, but never to the extent of those of
Derby oides nebrascensis. This thickening, together with the closely spaced external
lamellae it the shell margin, indicates periodic mantle retraction. This process
increased both the thickness of shell substance and the total depth of the shell
without appreciable increase to shell length or width.
The development of the dental and median ridges is informative in indicating the
affinity of these shells with stratigraphically younger forms, and helps to confirm
the interpretation by Williams (1965 : 11404) of the delthyrial chamber of Orthotetes
Fischer de Waldheim. The low trifid median ridge, which separates the ventral
adductor scars from the diductor scars, arose umbonally and fused with the posterior
ends of the dental ridges as a result of secondary shell deposition (Text-figs. 21-26).
Shell deposition in adult stages increased the depth of the dental ridges until they
approached the floor of the valve posteriorly (Text-fig. 26). Continued shell de-
position umbonally could have buried the posterior ends of these ridges, together
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
37
with the median ridge, so that in cross-section the ventral beak might appear to
possess a thick " pseudospondylium ".
A study of dorsal interiors varying from 1-5 mm. to 55 mm. wide shows certain
changes in the cardinalia. The angel of the socket plates to the hinge-line varies,
tending to decrease slightly with age. In an assemblage of variously sized shells the
1mm.
21
1mm.
22
1mm.
23
2 mm.
1 cm.
25
FIGS. 21-26. Illustrations of the ontogeny of the pedicle valve interior of Brochocarina
wexfordensis (Smyth), postero- ventral aspect, showing the fusion of the dental ridges
with the median septum, a, adductor scar; d, diductor scar; d.r, dental ridge; psd,
pseudodeltidium; t, tooth; v.i, ventral interarea.
angle is commonly between 20° and 25°. The smallest shells show scarcely any inter-
area, the cardinal process is but slightly differential into two lobes, the socket plates
are straight, (PI. 5, figs. 20, 21) and there are only the slightest lateral swellings in-
dicating the origins of the chilklium. By a width of 4-5 mm. all the essential elements
of the cardinalia are distinguishable, save for the median ridge and ventral node
between the cardinal process lobes and the slight thickening between the socket plates,
bounding the postero-median edges of the subcircular adductor field (PI. 5, fig. 22).
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
TABLE 8
No. of ribs
4
5
6
7
8
A
0
4
6
3
3
B
2
5
3
I
o
TABLE 8. The number of ribs counted in 2-5 mm. at 5 mm. (A) and 10 mm. (B) antero-
medianly of the dorsal umbo of Brochocarina wexfordensis (Smyth).
TABLE 9
J mm. (var.) = 6-33 (77'°93)
w mm. (var.) = 10-03 (213-866)
r = 0-998
a (var.) = 1-666 (o-ooin)
w mm. (var.) = 10-03 (213-866)
s mm. (var.) = 2-63 (8-032)
r = 0-997
a (var.) = 0-194 (0-000023)
TABLE 9. Statistics of length (1), maximum width (w) and maximum width of the socket
plates (s) of 12 dorsal valves of Brochocarina wexfordensis (Smyth) from Co. Fermanagh.
TABLE 10
1 mm. (var.) = 26-60 (70-203)
w mm. (var.) == 38-61 (137-950)
r = 0-983
a (var.) = 1-402 (0-01114)
TABLE 10. Statistics of length (1) and maximum width (w) of 8 pairs of measurements
from type dorsal valves of Brochocarina wexfordensis (Symth) from Hook Head, Co.
Wexford.
TABLE n
I mm. (var.) = 9-56 (122-115)
w mm. (var.) = 12-96 (226-31)
r = 0-994
a (var.) = 1-361 (0-00079)
I mm. (var.) = 9-56 (122-115)
E mm. (var.) = 1-29 (1-652)
r = 0-956
a (var.) = 0-116 (0-00042)
fi mm. (var.) = 1-29 (1-652)
cl mm. (var.) = 1-83 (3-873)
r = 0-984
a (var.) = 1-531 (0-00268)
TABLE n. Statistics of length (1), maximum width (w), height of delthyrium (h) and width
of delthyrium (d) at the anterior margin of the interarea of 16 pedicle valves of Brocho-
carina wexfordensis (Smyth) from Co. Fermanagh.
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 39
fOrthotetinid gen. and sp. indet.
(PI. 7, figs. 1-7)
Three distinctive cardinalia have been recovered from the etched limestones of the
Sillees River, Bunnahone, but no pedicle valves are known. Fortunately the three
vary in size, viz. total widths of socket plates = 4-7 mm., 14-1 mm. and 17-6 mm.,
allowing ontogenetic changes to be observed. These cardinalia are quite unlike other
davidsoniacean species from the faunas and are unusual in their slight strophomen-
acean characteristics, i.e. external ornament and strong dorsal median septum. A
cardinalia figured by Davidson (1861, pi. 27, figs. 6, 7) from Settle, Yorkshire is
probably conspecific, but was included as Streptorhynchus crenistria; otherwise
comparable material does not appear to have been described.
The brachial valve was apparently gently convex with a wide straight hinge-line,
well developed anacline interarea and arching chilidium from below which the
cardinal process projected strongly. The external ribbing occurs with a frequency
of about 10 ribs in 5 mm. width, 5 mm. from the umbo, and is apparently parvico-
stellate. Between the ribs is a less distinct concentric ornamentation of minute
ridges (PI. 7, fig. i), similar to that of strophomenaceans.
Internally the cardinal process is typically davidsoniacean with two well developed
incised lobes between which is a chilidial ridge terminating ventrally in a node. The
socket plates are strongly recurved and nearly parallel to the interarea; medianly
they merge to the cardinal process and prominent median septum, which is present
even in the smallest specimen.
The lack of pedicle valves make it impossible to be quite sure of familial placing
but the form of the socket plates indicates either the Schuchertellinae or Ortho-
tetinae as the most likely subfamilies. Of these the latter group seems more appro-
priate as some members of the Orthotetinae have a poorly developed dorsal median
septum. Until more material is available, in particular matching pedicle valves, a
full generic or specific designation will not be attempted.
Family SCHUCHERTELLIDAE Williams 1953
Subfamily SCHUCHERTELLINAE Williams 1953
Genus SERRATOCRISTA nov.
DIAGNOSIS. Shell small, commonly ventribiconvex, pedicle valve strongly curved
to conical in young shells ; hinge-line straight, commonly approximating to maximum
width; ventral interarea elongate, apsacline to catacline, pseudodeltidium arched
and entire, perideltidium obscure; dorsal interarea and chilidium much reduced;
radial ornament multicostellate, spinose with costellae regularly intercalated;
teeth supported by low dental ridges; muscle scars indistinct, rarely with slightly
raised lanceolate adductor scars; cardinal process low, bilobed and supported by
widely divergent socket-plates at about 25° to hinge-line; adductor field obscure,
shell substance probably pseudopunctate.
TYPE SPECIES. Serratocrista fistulosa sp.n.
40 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
DISCUSSION. Serratocrista is included in the subfamily Schuchertellinae on
account of its typically schuchertellid dorsal interior, including socket plates which
diverge from the hinge-line acutely and which recurve slightly at their antero-
lateral extremities. This is in contrast to the socket plates typical of the Strepto-
rhynchinae, which diverge from the hinge-line less acutely, at 50° to 60°, and continue
antero-laterally fused to the brachial valve floor with no recurvature towards the
posterior margin. Serratocrista differs from Schuchertella Girty, in being pseudo-
punctate and having no dorsal median ridge, features which recall Orthopleura
Imbrie, although it differs from this genus in being multicostellate and " spinose" .
Unlike Schuchertellopsis Maillieux, representatives of the new genus were not com-
pletely cemented by their pedicle valves to a foreign body during their life.
Serratocrista fistulosa sp.n.
(PI. 6, figs. 1-12)
DIAGNOSIS. Biconvex Schuchertellinae bearing spinose, strong ribs; chilidium
obsolescent, weak dental ridges and poorly impressed muscle scars.
DESCRIPTION. Outline transversely semi-oval, approximately two-thirds as long
as wide; biconvex, one-third as thick as long, slight dorsal median sulcus; strongly
multi-costellate bearing about four crestal " spines " medianly between 9 and 10 mm.
from dorsal umbo. About eight ribs occur per 2-5 mm. width antero-medianly at
5 mm. from dorsal umbo, pedicle valve costae commonly slightly stronger than
costellae; ventral adductor scars posteriorly placed, lanceolate, enclosed by slight
ridges; cardinal process low, lobes well separated by sulcus, socket plates diverge
from hinge-line at about 25°, prominent anteriorly, reaching almost one-third width
of hinge-line; sockets arched postero-medianly by antero-lateral growth of vestigial
chilidial plates; median septum absent, adductor scars obscure.
MEASUREMENTS (in mm.) :
length width
HOLOTYPE. Complete shell (66.52739) 14-4 18-0
PARATYPES. Complete brachial valve (66.52740) 9-6 14-6
Complete pedicle valve (66.52741) 14-1 20-0
Complete pedicle valve (66.52744) 3-6 5-1
TYPE LOCALITY. Sillees River, about 300 yds. east of 6unnahone Lough (low
D zone).
DISCUSSION. The costellate ornamentation is distinctive with its short pointed
" spines " commonly arising alternately from the crests of the ribs (PL 6, fig. 3).
These " spines " become slightly more widely spaced anteriorly, but medianly be-
tween 9 and 10 mm. from the umbo there are about four. Costellae were added by
branching and intercalation, although the latter is rare on pedicle valves and the
branching is predominantly median in origin. The costellae approximate to the
size of the costae within about 5 mm. of their origin. At 5 mm. from the umbo 3, 3
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 41
and 9 valves have 6, 7 and 8 ribs per 2-5 mm. width antero-medianly. The ribbing
is prominent with rounded crests and straight or slightly concave sides, up which
fine growth-lines can be traced (PL 6, fig. 3), and both wave-length and amplitude of
the ribs are commonly about equal. The radial ornamentation is comparable to
that of the mid Devonian European species Xystostrophia umbraculum (Schlotheim) ;
both species developed spinose outgrowths from their ribs, but in other respects,
such as cardinalia, the two are quite distinctive.
The shell interiors are unusually featureless, despite secondary thickening; the
dental ridges show no accentuation with increased age, nor is there any sign of a
median ridge in either valve.
Although described as pseudopunctate, the shell structure is a little uncertain.
The internal surfaces, of pedicle valves in particular, are covered by small pits which
are confined neither to ribs nor interspaces. Unfortunately, unsilicified material is
not available so microscopic examination of unaltered shell is impossible. One
incompletely silicified specimen is broken across the ventral interarea and part of the
valve. The inner and outer surfaces are completely silicified but internally there
is only a silica lattice comprising lamellae held by more or less perpendicular fine
rods (PI. 6, fig. n). This structure may be interpreted as being selective silicification
along planes in the original shell structure which represented a form of punctation
and the shell lamellae. Thomas (1958) describes Permian Streptorhynchus from
Western Australia as having a shell structure that differs from his other David-
soniacea. The conical flexures of the shell lamellae are directed outwards, rather
than inwards as in normal pseudopunctate shells, and Thomas suspects that these
flexures surrounded a fine canal (Thomas 1958, pi. 19). In the Australian material
this " punctation " was confined to the ribs, as is the internal punctation of many
enteletaceans and terebratuloids.
If the shell structure of the Fermanagh material was comparable it would explain
the minute pits on internal surfaces and could explain the selective silicification of the
shell figured in Plate 6, fig. n.
TABLE 12
I mm. (var.) = 10-83 (i7'53<>) I mm- (var-) = I0'^3 (*7'53o)
wmm. (var.) = 14-52 (31-078) tn mm. (var.) = 3-02 (0-654)
r = 0-970 r = 0-893
a (var.) = 1-332 (0-0262) a (var.) = 0-193 (0-0022)
TABLE 12. Statistics of length (1), maximum width (w) and thickness (th) of 6 pedicle
valves of Serratocrista fistulosa sp. n.
TABLE 13
I mm. (var.) = 5-75 (12-22)
w mm. (var.) = 8-33 (23-551)
r = 0-988
a (var.) = 1-389 (0-0058)
TABLE 13. Statistics of length (1) and width (w) of 10 brachial valves of Serratocrista
fistulosa sp. n.
42 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
Family MEEKELLIDAE Stehli 1954
Subfamily MEEKELLINAE Stehli 1954
[= Omboniinae Sokolskaja 1960]
Genus SCHELLWIENELLA Thomas 1910
TYPE SPECIES. Spirifera crenistria Phillips 1836, by original designation of
Thomas (1910 : 92).
Schellwienella radialis (Phillips)
(PI. 6, figs. 13-24. Text-figs. 27-35)
1836 Spirifera radialis Phillips: 220, pi. n, fig. 5.
1861 Streptorhynchus crenistria var. radialis (Phillips) Davidson: 129, pi. 25, figs. 16, 17, 18.
1930 ^Schellwienella aS. aspis Smyth: 555, pi. 16, figs. 6a, 6b.
1934 ? Schellwienella aspis var. radialiformis Demanet: 85, pi. 7, figs. 6-12.
DIAGNOSIS (emended). Dorsibiconvex to slightly resupinate Schellwienella with
strong parvicostellate ribbing, strong divergent dental plates, small complete
chilidium, high cardinal process and deeply impressed dendritic dorsal adductor
scars in adult.
DESCRIPTION. Profile inequibiconvex, adult brachial valve strongly convex
posteriorly, thickness about one-half shell width ; shell length about three-quarters
width, adult anterior margin commonly slightly uniplicate; ribbing unevenly
parvicostellate, commonly with seven ribs per 2*5 mm., 5 mm. antero-medianly of
dorsal umbo, costae consistently stronger than intercalated costellae; concentric
lamellae, becoming crowded marginally; ventral interarea apsacline, pseudodelti-
dium arched, perideltidium indistinct ; dorsal interarea short with chilidium of equal
length; dental plates receding, diverging to floor of valve, posteriorly enclosing
muscle field consisting of postero-medianly placed adductor scars flanked by pair of
rounded triangular diductor scars; cardinal process prominent, wide and bilobed;
socket plates at about 50° from hinge-line and curved to valve floor to enclose
sockets ; in adults ridges extend from socket plates to enclose oval dendritic adductor
scars separated by slight median ridge; shell substance sparsely pseudopunctate.
MEASUREMENTS (in mm.) :
length width
HOLOTYPE. Brachial valve (£.2054) c. 30-0 0.42-0
Incomplete brachial valve (66.52746) c. n-8 c. 15-4
Complete brachial valve (66.52747) 30-6 42-0
Incomplete brachial valve (66.52748) c. 30-8 c. 40-0
Crushed, incomplete shell (66.52750) c. 50-0 c. 59-0
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 43
TYPE LOCALITY AND HORIZON:
Holotype — in the University Museum, Oxford; No. £2054 collected by Phillips
from the " Base of the upper Irish limestone " at Florence Court, about 12 miles
S.E. of Derrygonnelly, Co. Fermanagh.
Other specimens from the argillaceous limestones and shales of Bunnahone and
Carrick Loughs, 2 miles N.W. of Derrygonnelly, Co. Fermanagh, or from underlying
shale | mile upstream from Milltown Bridge, I mile N.W. of Church Hill, Co.
Fermanagh. Low D. zone.
DISCUSSION. Although Thomas (1910 : 126) recorded the type material of
Spin/era radialis Phillips as having been lost, the specimen figured by Phillips
(1836, pi. n, fig. 5) is actually preserved in the University Museum, Oxford, No.
£.2054 and another specimen, No. E.2055, is possibly the second mentioned by
Phillips on p. 220 as coming from Cumberland, but it is not as well preserved as the
type specimen from Florence Court, Co. Fermanagh. Phillips described the Flor-
ence Court locality as being at the " Base of the Upper Irish limestone ", which is
the lateral equivalent of the " reefal " limestones about 12 miles N.W., near Derry-
gonnelly, from below which the present material was collected. The lithology and
fauna associated with the type specimen closely resembles the more shaly beds
underlying the limestone horizon at Bunnahone from which the silicified fauna was
collected. The type specimen itself shows only part of the dorsal exterior (PI. 6,
fig. 24), but in all known details it is closely comparable with the schellwienellas
recovered from Bunnahone and for these reasons the horizons are considered com-
parable and the forms conspecific.
Thomas (1910 : 126) referred Spin/era radialis, " as ascribed by some British
authors " to Schuchertella, a view followed by Demanet (1934 : 87) and Sarycheva &
Sokolskaja (1952 : 43). One of Davidson's figures, (1861, pi. 25, fig. 17) however,
clearly shows schellwienellid dental plates in an illustration of Streptorhynchus
crenistria, var. radialis from Gare, Lanarkshire, and it is probable that all three
figures, viz. 16, 17 and 18, are of Schellwienella radialis. Short, but well developed
dental plates are clearly visible in the Fermanagh specimens . (Text-figs. 27-30,
PI. 6, fig. 17)
The differentiation between costae and intercalated costellae is clear in shells
longer than 5 mm. The ribs are adorned by short dart-like projections, usually
arranged alternately, one on either side of the rib crest, with a modal frequency of
3 per mm. between 4 and 5 mm. from the umbo. There is no clear correspondence
between these serrations and the growth-lines, but the latter do project forward in
crossing each rib, showing that growth was more rapid in this region (PL 6, fig. 19).
In order to have maintained a more or less equally developed anterior margin,
without greatly extended ribs, the mantle must have retracted more strongly at the
rib crests than between them where shell deposition would have continued more
evenly. This retraction of the mantle probably resulted in the formation of the
spinose serration. The ornament contrasts with the undifferentiated ribbing
arrangement of Schellwienella aspis Smyth, from Hook Head, Co. Wexford, in rocks
of K, Z and C age. Smyth (1930 : 555), however, says that there is a tendency for
44
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
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Jii*
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SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
45
the costae of specimens from the strata of C age to be stronger and for "... every
fourth one to be emphasized ". Thus, it is possible that the ornamentation became
more differentiated through strata of C and S age to that seen on S. radialis in Upper
S and D strata.
The chilidium is well formed and in a brachial valve n mm. long was 2-7 mm.
wide and 0-3 mm. long (Text-fig. 32) arching over the posterior face of the cardinal
process in a postero-dorsal direction. A rudimentary chilidium can be distinguished
1mm
35
FIGS. 31-35. Illustrations of Schellwienella radialis (Phillips) showing the morphology
of the external radial ornamentation, (Fig. 31); the chilidium of young and adult
specimens (Fig. 32); a lateral view of an adult shell and the rotation of the juvenile
portion of the shell (stippled) relative to the hinge line (Fig. 33); and the cardinalia,
viewed dorsally, in young (Fig. 34) and adult (Fig. 35) specimens, i, costae; 2, first
order costellae; 3, second order costellae; a.r, ridge surrounding the adductor scars;
ch, chilidium; m.r, median ridge; s.p, socket plate.
46 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
in valves only 2-5 mm. wide, as bulbous projections postero-laterally of the cardinal
process lobes, similar to those seen in Brochocarina wexfordensis. During growth
the distal edge of the chilidium became directed posteriorly and finally ventrally.
This resulted not so much from a differential growth of the chilidium itself but by
the progressive rotation of the dorsal hinge-line resulting from increasing valve con-
vexity (Text-fig. 33), and the considerable thickness of secondary shell at the an-
terior margins of gerontic valves. This angle of rotation may exceed 90° and in a
specimen 52 mm. long approaches 110°. The cardinalia is typically davidsoniacean
in young shells (Text-fig. 34) but became considerably thickened in old age. In
adult shells the anterior face of the cardinal process became thickened so as to
extend beyond the youthful socket plates, leaving a distinct groove between the
two. The socket plates extend antero-laterally from the hinge-line at about 45° to
55° enclosing the sockets medianly. Although the bases of the socket plates curve
to the valve floor to bound the sockets antero-dorsally, they do not recurve towards
the hinge-line as in Orthotetinae. In shells more than about 40 mm. wide shell
deposition formed ridges which extended from the socket plates around the adductor
field. Postero-laterally within each adductor scar is an oval area, about one-third
as long as the complete scar, which has a differentiated ornamentation and may have
been the scars of posterior adductor muscles (PL 6, fig. 22).
In comparing the socket plates of different davidsoniacean subfamilies it must
be recognized that while those of the Meekellinae are described as prolonged, as are
those of the Streptorhynchinae and Derbyiinae, they do curve to the valve floor in
a manner similar to the Schuchertellinae. However, the socket plates of the
Schuchertellinae diverge from the hinge-line at a narrower angle than do those of the
Meekellinae, while in the Orthotetinae they recurve towards the hinge-line with
little anterior fusion to the valve floor.
Superfamily GHONETACEA Bronn 1862
The chonetacids are not considered to be a separate suborder, but to be sufficiently
closely related to the Productacea to belong to the suborder Productidina. Muir-
Wood (1962) discussed the classification of the chonetacids and followed her earlier
works of 1955, and with Cooper 1960, by separating them from the Productacea in
the belief that productaceans never had a functional pedicle. This has been shown
to be incorrect (Brunton 1965) and at least some genera of both groups had functional
pedicles during their earliest stages of ontogeny. A pedicle sheath was previously
unrecorded from chonetacids above the Devonian but is now described in Fermanagh
rugosochonetids and globosochonetids of Visean age.
It seems probable that Sarycheva & Sokolskaja (1959) are correct in uniting the
Chonetacea and Productacea and their revertion to the previously held view that
the Productacea were derived from the Chonetacea warrants careful consideration.
The two groups are united by a comparable gross morphology, pseudopunctation and
spine development and also by a similar phylogenetic trend to gigantism in the
Lower Carboniferous. This may indicate a response to certain conditions by groups
of organisms having arisen from the same ancestral gene pool. Probably during the
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 47
Devonian period the Productacea and Strophalosiacea differentiated from a choneta-
cean-like stock and rapidly diversified.
The plectambonitaceans possibly provided the ancestral stock from which the
chonetacids arose, possibly late in the Ordovician. Some of the earliest stropho-
chonetids, from Anticosti Island, Canada, are from beds commonly correlated with
the Upper Llandovery or Lower Wenlock. Eochonetes advena Reed, described
from the Upper Ordovician, Dnimmuck Group of Girvan, is plectambonitid in
character but had hollow canals, passing from the interior towards the exterior of
the posterior margin, which closely resemble the canals leading to the spines of
Chonetacea. It is not known whether the canals of Eochonetes extended to the
outer surface, and spines are unknown. But it is no great evolutionary step for the
epithelial processes, or evanginations, already present in Eochonetes to have remained
generative at their tips and to have grown posteriorly, accompanied by the de-
position of shell so as to have formed spines.
Rib apertures have been observed and figured from the time of Davidson's mono-
graph (1861) to Muir- Wood's recent chonetoid monograph (1962) in which she
follows Dunbar & Condra (1932) in assuming that they are the bases of minute
hollow spines. Muir- Wood (1962, pi. 6, fig. 6) illustrates the impression of the pedicle
valve of a rugosochonetid which is said to show " spinules ". However, inspection
of the specimen (66.20424) shows that fragments of shell adhere to the mould from
which taleolae or endospines protrude. Besides these there are fine obliquely
disposed ridges of sediment aligned along the rib impressions. These are the
sedimentary infillings of the rib apertures (" spinule bases "), but neither they nor
the taleolae are " spinules " protruding from the outer shell surface. A similar
phenomenon has been recorded by Demanet (1934 : 52) on moulds of Schizophoria,
where infillings of the punctae by iron oxides have left a minutely spinose surface.
On no specimens, either from Fermanagh or those studied by Davidson (1884, pi. 20,
fig. 21), have actual " spinules " been observed and it seems more likely that a rib
aperture was never the base of a true spine. The formation of the apertures pro-
bably took place by the sporadic inward sag of the mantle edge from the shell sur-
face, and the resulting oblique hollows became sealed at their inner ends by the
deposition of secondary shell. Anterior to each aperture, as growth continued, the
rib regained its shape by the reversion of the mantle edge to its normal folded con-
dition.
The morphology of the chonetacid hinge spines has attracted attention and it is
generally agreed that their formation was as described by Williams (1956 : 252).
However, Muir- Wood (1962 : 5) considers that chonetid spines differ from pro-
ductacid spines in that the latter were open at their distal end. Evidence in support
of this inference is lacking and it seems more reasonable, since the spines of both
groups were capable of growth, that the distal ends were sealed by the generative
tip of epithelium, covered by periostracum. The angle of emergence of the spines
from the hinge-line varied during the growth of the shell and they commonly curved
so that the distal part of the spine was at a different angle from that at which it
arose from the posterior margin. The early formed, more medianly placed spines,
tend to have a higher angle to the hinge-line than have those towards the lateral
48 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
extremities. A feature of spine orientation, noted on the Fermanagh shells, is that
the spines commonly extended posteriorly at the time of their origin. As a result
of valve curvature, and consequent rotation of the shell relative to the substratum,
the spines did not all grow parallel to the adult commissural plane. Thus, on adult
shells the median spines may be dorsally directed while those towards the lateral
extremities are progressively more posteriorly directed. This pattern of spine
growth probably assisted in the stabilization of the shells on the substratum through-
out life and after the pedicle had ceased to be functional.
Superfamily CHONETACEA Bronn 1862 nom transl. Shrock & Twenhofel 1953
Family CHONETIDAE Bronn 1862
Subfamily ANOPLIINAE Muir-Wood 1962
Genus GLOBOSOCHONETES nov.
DIAGNOSIS. Small, strongly concavo-convex Anopliinae with strong ribbing
and pair of ventrally serrated, anteriorly divergent septa in brachial valve.
DESCRIPTION. Shell small, outline semi-elliptical with rounded prominent umbo,
hinge-line widest part of shell; profile highly concavo-convex, medianly arched,
adult shells with four pairs of spines at high angle to hinge; young furnished with
pedicle sheath; multicostellate, commonly comprising sixteen costae branching
dichotomously or with rarely intercalated costellae, ribs rounded and more pro-
minent on pedicle valve ; ventral interarea orthocline, narrow with open delthyrium
and indistinct arched apical pseudodeltidium, dorsal interarea rarely developed;
teeth short and poorly differentiated from ventral interarea; median septum high,
posteriorly confined but commonly extended anteriorly as low ridge for about one-
third valve length; radially arranged tubercles correspond to external intercostal
spaces ; cardinal process undifferentiated internally, externally with V-shaped myo-
phore laterally supported by elongate, low socket ridges, almost parallel to hinge-
line; short lateral septa variable developed; pair of high septa cross dorsal visceral
disc almost to anterior margin, at about 12° from mid-line ; adductor scars indistinct,
divided by lateral septa; radially tuber culate as dorsal valve; shell pseudopunctate.
TYPE SPECIES. Globosochonetes parseptus sp. n.
DISCUSSION. The small size of these shells, together with their great convexity
and pair of prominent plate-like accessory septa across the dorsal interior, are fea-
tures common to genera included by Muir-Wood (1962) in her subfamily Anopliinae.
Although these genera are all described as having smooth shells, save for growth lines,
she does appear to allow for costellation in her subfamilial diagnosis by saying "shell
normally smooth", (1962:32). Thus the new genus, Globosochonetes, is here
included within the Anopliinae and differs from Anoplia, Anopliopsis, Chonetina,
Notanoplia and Tornquistia in being strongly ribbed. The ribbing and arrangement
of internal tubercles is intimate, so that while the latter are more or less scattered
within smooth genera, they are radially arranged in Globosochonetes. The genus
differs from Plicochonetes , of the Rugosochonetinae, with which it may have been
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 49
confused in the past, by its poorly differentiated cardinal process, strong dorsal septa,
finer ribbing and smaller size.
Globosochonetes parseptus gen. et sp. n.
(PI. 7, figs. 8-27, Text-figs. 36-41)
DIAGNOSIS. As for genus.
DESCRIPTION. Small, deeply convex shells, one-third as deep as wide, four-fifths
as long as wide, with narrow body cavity; ventral umbo of young shells flattened
or grooved, provided with supra-apical pedicle sheath ; costation rounded, even and
prominent except on umbones, costellae commonly dichotomously branched within
first 2 mm. of ventral beak; five ribs occur in i mm. width, 2 mm. antero-medianly
from ventral umbo ; adult hinge-spines slightly recurved towards mid-line, increasing
in size laterally, ventral median septum prominent and thickened in beak adjacent
to cardinal process; adductor scars oval, posteriorly placed, flanked by anteriorly
spreading diductor scars; poorly differentiated cardinal process with small alveolus
bordered by median ends of socket ridges that extend about one-half valve width and
enclose shallow sockets; lateral septa indistinct, at about 45° to hinge-line and
separate poorly defined posterior adductor scars from anterior adductor scars;
pair of high accessory septa diverge from mid-line at 10° to 15°, serrated distal edges
commonly exaggerated in geronitc shells; small, posteriorly placed, lobate median
septum developed late in life.
MEASUREMENTS (in mm.) :
length width
HOLOTYPE. Complete shell (66.52751) 3-1 4-1
PARATYPES. Complete pedicle valve (66.52752) 3-5 4-8
Incomplete brachial valve (66.52753) 2-7
Complete brachial valve (66.52755) 1-3 1-6
Incomplete pedicle valve with pedicle
sheath. (66.52756) 3-5
Incomplete pedicle valve with pedicle
sheath. (66.52757) 1-7
Incomplete brachial valve (66.52754) 3-9
Complete shell (66.55498) 3-7 4-4
6rachial valve (66.55499) c. i-g c. 2-6
Incomplete shell (66.55783) 3-1 3-6
TYPE LOCALITY. Sillees River, about 300 yds. east of 6unnahone Lough (low
D zone).
DISCUSSION. Two small specimens in the Davidson Collection of the 6ritish
Museum (Nat. Hist.) (6.14174) from Settle, Yorkshire, which are possibly the
originals for figure 18, plate 47 of Davidson (1861), are externally indistinguishable
from the Fermanagh shells. 6oth have the same shape and rib counts. Although
GEOL. 1 6, I. 4
50 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
the interiors of the Davidson specimens are not known, they are thought to be con-
specific with G. parseptus.
The Fermanagh species is apparently similar to Chonetes minuta Goldfussi sensu
de Koninck (1847 : 219, pi. 20) from the Devonian Eifel region. However, C.
minuta is longer (length is given as 12 mm. by de Koninck) and the ribbing apparently
more coarse, i.e. 22 ribs in all. G. parseptus is comparable in size and shape to
Leptaena (Chonetes) subminima M'Coy. However, inspection of the type specimens
from the Sedgwick Museum, Cambridge (£.6773-6780) shows that M'Coy's species
has a finer costellation, viz. about 14 ribs per one mm., i mm. antero-medianly from
the ventral umbo (cf. Table 14). The poorly preserved dorsal interior shows no sign
of the strong septa present in the Fermanagh species and the two are not con-
specific. Neither is M'Coy's material conspecific with the specimen " from the
Namurian of the river Hodder, Yorkshire ' ' (6.53889) which Muir-Wood (1962 : 62)
tentatively identified as "Chonetes [IPlicochonetes] subminimus (McCoy) ". The
Hodder specimen has a rib count similar to that of G. parseptus and the two could
be congeneric.
Tornquistia polita (M'Coy) resembles the new species in size, shape and dorsal
interior but differs in being devoid of all ribbing.
Muir-Wood (1962 : 6) speaks of the young of some Devonian and Silurian chonetids
having been attached by a pedicle which emerged through the ventral umbo and
formed a " small pedicle pipe ". The present Visean chonetids are probably the
first of this age to be recorded showing the structure, here called the pedicle sheath.
It was almost certainly not functional in valves 3 mm. long because the ventral
beak of such valves is filled by secondary shell at the posterior end of the median
septum. With a maximum diameter of only about 0-03 mm., it is unlikely that the
pedicle was functional for long after the spat had settled, or that its growth con-
tinued beyond the neanic stage : certainly no internal opening has yet been distin-
guished in valves longer than 1-2 mm. The pedicle sheath is essentially the same
structure as is seen in several genera of the productacea, and it does seem that a
functional pedicle was more common in the early stages of brachiopod development
than is often supposed. Unlike Muir-Wood (1962 : 6) the writer considers the ped-
icle sheath to be a feature of both strophomenoids and productoids, and one which
indicates the close relationship of the two groups.
During growth, the rate of shell deposition appears to have been greatest on the
flanks, so that the pedicle valve became highly arched medianly and in these regions
occurred the greatest proliferation of the costae. In some shells this pattern of
growth led to a slight flattening of the antero-median venter. Costae are absent from
the first 0-5 mm. of the shell and less prominent upon the brachial valve. 2, 6, 12, i
and i specimens have respectively 14, 15, 16, 17 and 18 costae. Branching most
commonly occurred within the first 1-5 mm. from the pedicle beak and was usually
of a dichotomous nature, especially on the pedicle valve. However, about three-
fifths of the costellae of both valves were added by external, (i.e. lateral) branching
or by intercalation, and any one specimen may show all these types of rib addition.
Of the four pairs of hinge-spines, the last formed are the largest, and although they
arose from the hinge-line at an angle of about 120°, they soon curved inwards to
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 51
become parallel or even convergent to the mid-line. As would be expected, the spines
arose at regular intervals, the third and fourth at valve lengths of about 2 and 3 mm.
respectively. The means (with variances) of the distances between the spines are
given in Table 15.
The first pair of spines were of very small diameter, like the pedicle sheath, and
were soon internally sealed. The second pair remain open in valves about 1-2 mm.
long, but beyond this size soon became closed by the antero-lateral growth of the
interarea and teeth. The third and fourth pairs of spines commonly retain their
internal connections, opening anterior of the interarea (PL 7, fig. 14). The teeth are
commonly indistinctly differentiated from the interarea by a slight ridge, although
in some specimens they are more distinct and diverge from the hinge-line at an angle
of up to 10°.
The ventral median septum is distinguishable in valves 1-2 mm. long, and arose
from the beak (Text-fig. 37). At this growth stage the adductor scars from a sub-
rounded, rather flat area within the ventral umbo. Beyond this stage convexity
was such as to reorientate the muscle field from being dorsally to anteriorly directed
and within these adult shells the adductor field is divided by the septum, which,
while remaining confined to the umbonal region, is extended anteriorly as a low
ridge for nearly one-third the length of the valve (measured parallel to the com-
missural plane).
The protegulal node is well seen on brachial valves, having been protected from
abrasion by the shell convexity. It is commonly 0-3 mm. in length and about one-
half the width, and is represented internally by the alveolus, lying between the car-
dinal process base, the socket ridges and the posterior ends of the strong accessory
septa, which are 0-15 mm. apart (Text- fig. 40). The septa are highest at about mid-
valve length and always have serrated distal margins, the serrations being anteriorly
directed and lobate in gerontic shells (Text-fig. 41). These septa were probably
supporting structures to the brachial apparatus and within these small shells may
have assisted in the separation of the water currents in the brachial cavity.
A short median septum can be distinguished in dorsal valves of about 2 mm. in
length. It continued to grow by secondary shell accretion over the median row of
tubercles so that in valves about 3 mm. long it extended nearly i mm. anteriorly
of the hinge-line. The alveolus always remained free of secondary structures
(PL 7, figs. 21, 26).
TABLE 14
Ribs
4
5
6
7
A
o
23
41
10
B
8
21
6
o
TABLE 14. The number of ribs counted in a width of i mm. at i mm. (A) and 2 mm. (B)
antero-medianly of the ventral umbo of Globosochonetes parseptus gen. et sp. n.
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
1mm.
39
FIGS. 36-39. Illustrations of the ontogeny of the pedicle valve of Globosochonetes par-
septus gen. et sp. n., Fig 36 is the external view of the same specimen as Fig. 37 within
which muscle scars, probably adductors, are clearly developed.
FIGS. 40-41. Brachial valve interiors of young and adult specimens of G. parseptus. The
depression anterior to the cardinal process of the young valve is represented externally
by the protegulal node.
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
TABLE 15
53
Between
Between
Between
Between
Between
Valve
umbo
and ist
ist and 2nd
2nd and 3rd
3rd and 4th
outer
spines
length
Mean (mm.)
(var.)
0-28
(0-0017)
0-40
(0-00069)
0-60
(0-0065)
0-74
(0-0125)
2-66
(0-190)
2-66
(0-266)
n.
30
30
27
5
30
30
TABLE 15. Statistics of the distances between hinge-spines (numbered outwards from the
umbo) of Globosochonetes parseptus gen. et sp. n., together with the total distance between
the outer pair of spines and the length of the valves.
TABLE 16
I mm. (var.) = 2-15 (0-266)
r = 0-946
w mm. (var.) = 2-61 (0-960)
a (var.) = 1-315 (0-00371)
TABLE 16. Statistics of length (1) and maximum width (w) of 51 pedicle valves of
Globosochonetes parseptus gen. et sp. n.
TABLE 17
I mm. (var.) = 2-30 (0-272)
w mm. (var.) = 2-89 (0-370)
r = 0-959
a (var.) = 1-171 (0-00427)
I mm. (var.) = 2-30 (0-272)
{fit mm. (var.) = 0-99 (0-060)
r = 0-895
a (var.) = 0-469 (000169)
TABLE 17. Statistics of length (1), maximum width (w) and thickness (th) of 28 shells of
Globosochonetes parseptus gen. et. sp. n.
TABLE 18
I mm. (var.) = 1-98 (0-216)
r = 0-729
s mm. (var.) = 0-52 (0-0147)
a (var.) = 0-263 (0-00088)
TABLE 18. Statistics of valve length (1) and the distance between the anterior ends of the
accessory septa (s) of 39 brachial valves of Globosochonetes parseptus gen. sp. n.
Subfamily RUGOSOCHONETINAE Muir-Wood 1962
Genus RUGOSOCHONETES Sokolskaja 1950
TYPE SPECIES. Orthis hardrensis Phillips 1841, pars, by original designation of
Sokolskaja (1950 : 23).
DISCUSSION. Diagnosis of the genus depends upon an understanding of R.
hardensis. The species was discussed by Muir-Wood (1962) who selected a lectotype
54 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
from amongst the Phillips specimens from Hardraw, Wensleydale, now at the
University Museum, Oxford, (£.1571). Neither this specimen nor the remaining
Hardraw specimens at Oxford are particularly well preserved, being moulds or
somewhat crushed specimens in shale. The lectotype, and two other specimens
(E.I577, 1578), show distinct lobate areas on either side of the mid-line presumably
accentuated by sediment compaction and slight crushing of the shell. These areas
exactly match elevated regions seen on the dorsal interior of a specimen from Ray
Gill, near Hawes, Wensleydale (Geol. Surv. Mus. 95131), which are assumed to mark
the regions enclosed by the spirolophe. Further collecting is required to ascertain
whether this dorsal morphology is a consistent and specific feature. The similarly
sized specimens £.1569 (Univ. Mus. Oxford) and 66.41147 (British Museum (Nat.
Hist.)), figured by Muir-Wood (1962), show dorsal interiors without distinguishable
brachial areas and such specimens may prove to be distinctive.
In comparing the Fermanagh rugosochonetids with the types of R. celticus it
became apparent that the specimens assigned by Muir-Wood to this species belong
to three distinct groups. The holotype (36.41145) from Flintshire, North Wales,
(PL 7, figs. 28-31) together with other specimens from Flintshire and elsewhere in
Britain are distinguishable by their clear and fine ribs. Five, 25 and 8 specimens
have respectively 4, 5 and 6 ribs per mm. at 4 mm. from the ventral umbo. Muir-
Wood (1962 : 69) mentions a coarsely ribbed variant and these valves were figured
as being conspecific. Three, 10 and 4 specimens have respectively 2, 3 and 4 ribs
per mm. at 4 mm. from the ventral umbo (e.g. 6.53892 and 68475 in Brit. Mus.
(Nat. Hist.) (PL 8, figs. 2-5), and although they have been found at the same loca-
lities as the fine ribbed R. celticus s.s., appear to have other distinctive features.
The coarse ribbed shells have more prominent rib apertures and a relatively longer
ventral median septum than have the finely ribbed group, and the ventral adductor
scars are distinctive in being slightly raised above the floor of the valve.
The R. celticus picture is further complicated by specimens from Northumberland
and Fifeshire which are poorly ribbed (e.g. 6.42046, 66.41100-01 and 6.53929-34)
(PL 8, figs. 6-9). While the rib frequency is consistent with R. celticus s.s., the rib-
bing is absent postero-laterally, near the posterior margin, and commonly replaced
anteriorly, after a valve length of 7-9 mm., by irregular but prominent " growth-
lines ". This anterior region is commonly infested by boring organisms and it may
be that an ecological factor effected the growth of these shells. They further differ
by their slightly greater width, relative to length; flatter umbo and smoother
ventral diductor scars than in R. celticus s.s. Owing to the poorly developed ribbing,
the internal valve margins are not strongly crenulated.
The distinctions between R. celticus and R. hardrensis are slight. Muir-Wood
(1962 : 70) says that the former is larger, more convex in profile, has spines extending
from the hinge at a lower angle, and " has slight internal differences " from R.
hardrensis. The few complete shells assigned to R. hardrensis from the Hardraw or
Gayle shales of Wensleydale that are available for study (Geol. Surv. Mus. 93151-
93152; 8rit. Mus. (Nat. Hist.) 6.80965-80966, and 66.52661-52666) are almost
indistinguishable from the holotype of R. celticus. One Wensleydale specimen in
the Geological Survey Museum (93152) is 0-5 mm. longer and wider than the holotype
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 55
of R. cdticm and differs in shape by being almost 20 % thicker! The rib frequency
is 25 in 5 mm. at 5 mm. from the ventral umbo in both specimens. The difficulty
in comparison lies in the poor preservation of the R. hardrensis lectotype and in
deciding if this specimen is conspecific with the R. celticus-tike Wensleydale speci-
mens. If this were so R. celticus would be a junior synonym of R. hardrensis.
However, until a large localised collection can be studied to enable valid comparisons
to be made, the two species must remain. Within R. celticus Muir-Wood distinction
should be drawn between the finely ribbed holotype group; the coarsely ribbed
group and those with poorly developed ribbing. These groups may well warrant at
least subspecific designation.
Rugosochonetes silleesi sp.n.
(PI. 8, figs. 10-27; Text-figs. 42-50)
DIAGNOSIS. Rugosochonetes with strongly convex pedicle valve and prominent
umbo; multicostellate with 6 ribs per mm., 4 mm. from dorsal umbo, rib apertures
present.
DESCRIPTION. Outline semielliptical with length about two-thirds maximum
width, hinge-line straight; shell unequiconcavo-convex with rounded ventral umbo
extending beyond hinge-line, thickness approximately one-third hinge width;
hinge spines extend posteriorly at about 30° to median plane, seven pairs on adult
valves; multicostellate, ribs rounded, as wide as interspaces; about twenty-five
costae, costellae commonly added by intercalation on brachial valve and by dicho-
tomy on pedicle valve ; about six ribs per i mm. width, 4 mm. antero-medianly of
dorsal umbo, rib apertures sparsely developed; fine concentric growth-lines in-
distinct; ventral interarea anacline to orthocline, short, delthyrium quadrate to
triangular, pseudodeltidium apical, much reduced; dorsal interarea hypercline,
reduced, small chilidial plates flank notothyrium ; teeth set slightly below and parallel
to plane of interarea, grooved on ventral surfaces ; median septum high umbonally,
thickened below delthyrial apex, in adult shells extending one-third valve length as
low ridge ; ventral muscle field flabellate, adductor scars pear-shaped, diductor scars
elongately triangular, bounded postero-laterally by distinct shell thickening; hinge
spines commonly communicating internally through oblique canals; cardinal pro-
cess bilobed, poorly differentiated, myophores dorsally directed, V-shaped and in-
cised; cardinal process laterally supported by socket ridges at about 20° to hinge-
line, which enclose well defined sockets anteriorly; alveolus well defined; median
septum extends about one-half length of adult valve; lateral septa prominent
anteriorly, disposed at 30° to mid-line, and extending for about one-third length
of adult valve; dorsal muscle field indistinct, posterior and anterior adductor scars
pear-shaped and oval, separated by posterior ends of lateral septa; both valves
internally ornamented by anteriorly directed radial rows of tubercles corresponding
to external interspaces and pseudo-punctation, valve margins internally ribbed.
56 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
MEASUREMENTS (in mm.) :
length width
HOLOTYPE. Complete shell (66.52758) 9-6 12-6
PARATYPES. Complete pedicle valve (66.52759) 9-6 12-7
Incomplete pedicle valve (66.52760) 13-0
Complete brachial valve (66.52761) 9-1 14-4
Incomplete brachial valve (66.52762) 10-3
Complete brachial valve (66.52763) 2-8 3-9
Complete brachial valve (66.52764) 7-7 n-8
Complete shell (66.52766) 9-8 13-0
Complete pedicle valve (66.52765) 7-0 8-9
Incomplete pedicle valve (66.52767) 3*7 c. 4-9
Complete shell with pedicle sheath
(66.52768) 1-6 2-0
Shell crushed in shale (66.52769) c. n-i c. 17-2
Shell crushed in shale (66.55784) c. n-o c. 17-2
Incomplete shell (66.52770) 4-7
TYPE LOCALITY. Sillees River, about 300 yds. east of 6unnahone Lough (low
D zone)
DISCUSSION. The Fermanagh material is in general accordance with several
features described or illustrated by Muir-Wood for R. celticm (1962 : 68). However,
the shells only rarely reach the dimensions given by her, " about 19 mm. wide,
14 mm. long, and 3 mm. thick ", in the shales below the silicified limestone horizon
which yields the present sample. More important distinctions are in the proportions
of size and ribbing. Selecting 38 shells of R. celticus s.s. (i.e. holotype and con-
specific specimens with the fine ribbing taken from a number of localities, in the
6ritish Museum (Nat. Hist.) collections) 5, 25 and 8 specimens have respectively
4, 5 and 6 ribs per i mm. width, 4 mm. antero-medianly. This compares with 6,
20 and 3 specimens of R. silleesi having respectively 5, 6 and 7 ribs per mm. (Table
21). The thickness of the shell, compared to length, is consistently greater in R.
silleesi as a result of the deeper, more prominently rounded ventral umbo ; the rela-
tive shell length is also slightly greater. The shell outline underwent little change
during growth other than becoming relatively wider, although the cardinal ex-
tremities were usually obtuse and only rarely represented the widest part of the
shell. This variability seems to have resulted from an acceleration of growth in a
lateral direction during the formation of each pair of spines. The spines, which
number seven pairs in adult shells, arose with fairly regular spacing along the pos-
terior margin of the ventral interarea (Table 22). It is frequently impossible to
distinguish the sites of the first formed spines, and for this reason measurements were
always taken from the mid-line of the valve to the second pair of spines. However,
when the first pair were distinguishable, measurements were made and range from
0-35 to 0-6 mm., with a modal value of 0-4 mm. The spines become stronger later-
ally, the sixth pair commonly being about 0-2 mm. in diameter. Most spines are
inserted obliquely to the posterior margin of the valve but almost immediately
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
57
continued to grow posteriorly at a high angle from the posterior margin of the valve.
At each stage of growth the spines were posteriorly projecting so that in the adult
shell the oldest, median spines, are nearly dorsally directed, while the youngest,
lateral spines, project posteriorly (Text-fig. 42). This indicates the degree of rota-
tion relative to the hinge-line during growth. Most commonly the spines retained
hollow connection to the valve interior throughout adulthood (PI. 8, fig. 22). The
p.sh.
h.sp.
1mm.
43
FIG. 42. Posterior view of a rugosochonetid shell showing the way in which rotation
of the commissural plane relative to the horizontal led to a swing in the orientation of
the hinge-spines from being dorsally directed, medianly, to posteriorly directed, laterally,
in adult shells; y and o indicate the spine orientation relative to the hinge-line axis of
the spines formed in youth and old-age respectively.
FIG. 43. Illustration of a young rugosochonetid shell viewed postero-dorsally; h.sp,
hinge-spine; p.n, protegulal node; p.sh, pedicle sheath projecting from the tip of the
ventral umbo. The cardinal process is bilobed and a rudimentary chilidium is commonly
distinguishable.
lateral two or three pairs of spines have broad direct openings to the interior, antero-
ventral of the hinge-line, while the median three or four pairs retain connection by
obliquely disposed canals through the interarea, so as to open ventro-laterally of the
teeth. In a shell 13-0 mm. wide along the hinge-line, the second and third pairs
of spines have canals, 0-8 mm. long, running through the interarea at about 70° to
the mid-line.
The convexity of the pedicle valve is regular in the mid region, but there is flatten-
ing towards the cardinal extremities to form small ears. The brachial valve is
flat for the first i-o mm., around the prominent protegulal node (Text-fig. 43).
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
Beyond this length concavity of the valve is gentle and regular so as to meet the
pedicle valve towards the anterior margin as a short trail.
The radial ornament is equally conspicuous on both valves, although obscure for
about the first i mm. of both valves. The ribs are prominent, rounded and of much
the same wave-length as the interspaces, each one slightly increasing in size towards
the anterior margin. Table 23 shows the range in the number of costae observed on
,c.p.
46
FIGS. 44-47. Illustrations of principal internal morphological features of chonetids;
brachial valve (Fig. 44), pedicle valve (Fig. 45); a reconstruction of the postero-median
segment of the sylized lophophore and body wall supported by the lateral septa (Fig. 46);
and a lateral view of the lateral septa (Fig. 47), a.a, anterior adductor scar; a, ventral
adductor scar; av, alveolus; b i., brachial impression; b.w, body wall; ch, chilidium;
c.p, cardinal process; d, ventral diductor scar; /, stylized lophophore; l.s, lateral septum;
m.c, trace of a mantle canal; m.r, median ridge; m.s, median septum; p.a, posterior
adductor scar; s, socket; sp, spine; sp.o, internal spine opening; t, tooth.
brachial valves. The number counted on pedicle valves is consistently comparable,
and within the same range fo four. On the brachial valve costellae are most com-
monly added by intercalation ; this is almost invariably so over the median region
of the valve, but on the flanks sporadic dichotomy of the ribs is usual. Intercalation
is rare on the pedicle valves and dichotomy is the usual method of branching (Table
24). Thus the ribbing is complimentary and ventral dichotomy is usually accom-
panied by dorsal intercalation during growth. Muir-Wood (1962 : 9) wrote of the
" elongate-trigonal perforations " seen on the ribs of " most chonetids ", as being
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
59
the " base of small hollow spinules which were very fine and delicate and are rarely
preserved in place ". These apertures are irregularly and sparsely distributed on the
ribs of R. silleesi as anteriorly directed arches temporarily terminating the rib.
Anteriorly the rib regained its normal dimensions over a distance of less than
0-5 mm. (PL 9, figs. I, 2). The same sort of structure is to be seen on the ribs of
Schizophoria and Rhipidomella from the same locality. The apertures were formed
48
FIGS. 48-50. Stylized reconstructions of the musculature and inferred position of the
diagrammatic lophophore in Rugosochonetes silleesi sp. n. as seen in transverse section
from the anterior (Fig. 48), in longitudinal section (Fig. 49), and the brachial valve
interior (Fig. 50), a.a, anterior adductor muscle; d, diductor muscle; l.s, lateral septum
with its prolongation showing as a discrete position of shell between the dorsally divi-
ded adductor muscles; m.s, ventral median septum; p.a, posterior adductor muscle.
by the temporary retraction or sagging of the mantle edge from the inner shell sur-
face of the rib so that deposition ceased to form a rib until the mantle had once again
become folded. Muir-Wood has referred to the taxonomic importance of these
" spinulus ". Certainly there seems to be a genetical control within brachiopods
as a whole, governing the formation of these apertures ; a control which is of system-
atic importance amongst Lower Palaeozoic orthaceans and enteletaceans.
The ventral beak of young shells is grooved, in a similar way to that of Globoso-
chonetes, but a pedicle sheath is only rarely preserved (PI. 8, fig. 26). The median
60 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
septum was developed from the earliest stages, but only in shells longer than about
5 mm. is the median ridge developed anteriorly of the high umbonal septum.
Within the dorsal valve, the lateral septa, or anderidia of Sadlick (1965 : 157)
became prominent in valves more than 5 mm. long, prior to which the septa are
little more than raised tuberculate regions with a posteriorly placed ridge of about
0-3 mm. In adult shells the septa developed anteriorly forming distinct prongs.
From their anterior ends indistinct reniform areas, enclosed by a slight ridge or by
tubercles, can be seen extending beyond the median septum for about two-thirds of
the valve length (Text-fig. 44). The dorsal median septum is low and flattened,
except anteriorly (PI. 8, fig. 23). This flattening did not result from restriction with-
in the body cavity of the shell as the valves are well separated in this region. The
lateral septa (anderidia) are thought to have given support to the posterior ends of
the primary loop of the spirolophe (Text-fig. 46), which was itself partly supported by
the median septum and partly from the reniform markings antero-lateral of the
median septum. Such an arrangement of the brachial apparatus would have been
similar to that illustrated by Williams (1956) in fig. 5 (6) for Productus s.s. Text-
figs 48-50 show the inferred gross anatomy of the species. If this interpretation is
correct, the prolongations of the lateral septa (anderidia) protuded anteriorly of the
visceral cavity, as defined anteriorly by the inferred paths of the adductor muscles.
It is envisaged that the prolongations supported the anterior body wall at the points
from which the lophophore was supported. Sadlick (1965 : 158) describes the
anderidia as being in the coelomic cavity and well behind the body wall, and argues
TABLE 19
I mm. (var.) = 6-n (87144) I mm. (var.) = 6-n (87144)
w mm. (var.) = 8-02 (15-213) fn mm. (var.) = 2-29 (2-0567)
r = 0-992 r = 0-920
a (var.) = 1-321 (0-00073) a (var.) = 0-486 (o-oono
tn mm. (var.) = 2-29 (2-0567)
x mm. (var.) = 7-08 (12-039)
r = 0-972
a (var.) = 2-419 (0-00847)
TABLE 19. Statistics of length (1), maximum width (w), thickness (th) and width of hinge-
line (x) of 40 shells of Rugosochonetes silleesi sp. n.
TABLE 20
I mm. (var.) = 6-77 (1-422)
s mm. (var.) = 3-17 (0-739)
r = 0-959
a (var.) = 0-721 (0-00350)
TABLE 20. Statistics of length (1) and length of the median septum (s), measured from the
hinge-line, of 14 brachial valves of Rugosochonetes silleesi sp. n.
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
TABLE 21
61
No. of ribs
5
6
7
8
At 2 mm. from umbo
i
ii
16
2
At 4 mm. from umbo
6
20
3
O
TABLE 21. Ribs counted per i mm. width at distances of 2 mm. and 4 mm. antero-
medianly from the dorsal umbo of R. silleesi sp. n.
TABLE 22
Distances
between
spines
Umbo and
2nd
2nd and 3rd
3rd and 4th
4th and 5th
5th and
6th
6th and
7th
Mean (mm.)
0-90
0-74
1-018
1-22
1-26
i-35
(Var.)
(0-01214)
(0-0182)
(0-0395)
(0-0157)
(0-0257)
N
29
28
22
15
8
2
TABLE 22. Distribution of hinge-spines. Distances measured from the mid-line to the
second spine and subsequently between additional spines of R. silleesi sp. n.
TABLE 23
No. of costae on dorsal valves
20-23
24-27
28-30
No. of specimens
4
18
6
TABLE 23. The number of costae counted on 28 dorsal valves of Rugosochonetes silleesi
sp. n.
TABLE 24
Dichotomy
Median
Flanks
sector
Both
Brachial valves
19
2
2
30
Pedicle valves
30
4
TABLES 24. Scoring for the method by which costellae were added on 53 brachial valves
and 34 pedicle valves of R. silleesi sp. n.
62 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
that they could not have been used for lophophore attachment. While this is
agreed, nevertheless it is considered that these ridges developed functionally as
posterior supports to the lophophore and that in life the anteriorly projecting
processes were probably prominent in adult shells. Having restricted the anderidia
to the coelomic cavity Sadlick can hardly suggest that " long anderidia undoubtedly
helped form a channel for inhalent currents " (1965 : 158).
Rugosochonetes delicatus sp. n.
(PL 9, figs. 3-15, Text-figs 51, 52)
DIAGNOSIS. Gently concavo-convex Rugosochonetes with flattened ventral umbo,
thin-shelled; finely and indistinctly multicostellate with few rib apertures; muscle
scars obscurely developed.
DESCRIPTION. Outline subsemicircular, about two- thirds as long as wide,
greatest width at straight hinge-line with poorly defined triangular ears; profile
concavo-convex, pedicle valve evenly convex, umbo flattened, not extending
beyond hinge-line, thickness one-quarter to one- third length, body cavity narrow;
adult shells with four pairs of hinge-spines at 30° to 40° from mid-line; multi-
costellate, ribs low and rounded, umbones smooth, costellae rarely added by dicho-
tomy and intercalation, commonly 7 ribs per mm. width, 2 mm. or 4 mm. antero-
medianly of pedicle umbo; rib aperture sparse, growth-lines indistinct; ventral
interarea apsacline to orthocline, short, delthyrium open, pseudodeltidium reduced;
dorsal interarea one-third length of ventral interarea, chilidial plates small, arcuate ;
teeth subparallel to interarea, slightly crenulated distally; median septum short but
high, extending about i mm. across ventral umbo and separating indistinct flabellate
muscle field ; first 2 pairs of spine openings deflected laterally by semiconical screens
of secondary shell; cardinal process lobes more or less fused medianly, myophore
V-shaped, directed postero-dorsally and fused proximally ; deep alveolus flanked by
socket ridges at about 20° to hinge-line and extending about one-third its width;
lateral ridges short and low posteriorly; shell substance thin, pseudopunctate.
MEASUREMENTS (in mm.) :
length width
HOLOTYPE. Complete shell (66.52771) 6-5 8-5
PARATYPES. Complete pedicle valve (66.52772) 6-5 9-3
Incomplete pedicle valve (66.52773) 8-3
Complete damaged shell (66.52776) 3-6 c. 5-8
Complete shell (66.52774) c. 5-0 7-6
Complete pedicle valve (66.52775) 5-0 6-6
TYPE LOCALITY. Sillees River, about 300 yds east of 6unnahone Lough (Low
D zone).
DISCUSSION. The species is similar in estimates of relative length and thickness
to R. silleesi (Tables 19, 25) with which it occurs, and the two are probably closely
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 63
related. In other respects, however, there are persistent clear differences. Thus,
R. delicatus differs from R. silleesi in having a much flatter ventral umbo which does
not project beyond the hinge-line, which constitutes the greatest width of the shell.
The radial ornament, although of similar frequency, is less prominent, the ribs being
low and costellae added on the pedicle valve by intercalation and dichotomy rather
than almost entirely by dichotomy. The rows of tubercles are uniformly delicate
over the entire ventral interior, about 4 occurring per mm. on the lateral flanks,
whilst in this region of R. silleesi the tubercles are about twice the size with a
frequency of 2 or 3 per mm. The dorsal median septum is ill defined and perhaps
never fully developed. The body cavity is smaller and the shell substance thinner.
The poorly defined ribbing and its absence close to the posterior margin is similar
to the ornamentation of R. hindi Muir-Wood from the H zone of Cheshire, and to the
poorly ribbed specimens of R. celticus Muir-Wood typical of the low E zone of
Northumberland. However, the Fermanagh specimens differ from the former
species in being concavo-convex, having fewer spines per unit length of hinge-line
and in having 7 or 8 ribs per mm. at 4 mm. from the umbo as compared to 5 or 6
per mm. in R. hindi. The frequency of ribbing on 5, 13 and 5 specimens attributed
to R. celticus from Northumberland is 4, 5 and 6 ribs per mm respectively. 4 mm.
from the umbo. This frequency is comparable to that of R. celticus s.s., but is coarser
that that of the two Fermanagh species R. silleesi and R. delicatus.
The brephic shell was furnished with a supra-apical pedicle sheath (PL 9, fig. 14),
extending ventro-posteriorly, which arose from the tip of the pedicle beak and posterior
to the shallow V-shaped groove across the young shell. During growth each pair
of hinge-spines was inserted at fairly regular intervals and projected posteriorly in
the commissural plane at the time of their growth. As growth proceeded the com-
missural plane rotated clockwise relative to the substratum (as viewed laterally with
the umbo to the left) so that adult shells have their lateral spines directed posteriorly
and their median, early formed spines, project dorsally as in R. silleesi (Text-fig. 42).
Like R. silleesi, the spines retain their connection to the interior, but unlike that
species, the interarea is only slightly thickened so that instead of oblique canals
maintaining connection, localized deposits of secondary shell deflect the internal
openings laterally to positions comparable to those of R. silleesi (Text-figs 51, 52).
This deflection became less pronounced during growth so that younger spines have
more direct openings to the interior. A valve 9-3 mm. wide has its first formed
spines 0-5 mm. from the mid-line, but these do not open to the interior for a distance
of 1-2 mm. from the mid-line; at this distance the second spines occur and these open
internally 1-7 mm. from the mid-line.
The slight amount of secondary shell deposition has resulted in poorly developed
internal markings. The ventral muscle field has slight postero-lateral thickenings
at its margin, but the median septum is rarely continued as a median ridge. Only
two cardinalia are available for study and these have well developed socket ridges at
about 20° to the hinge-line, extending about one-third of the hinge-width ; the lateral
septa (anderidia) are clearly distinguishable, having raised prolongations anteriorly
which are considered to have supported the posterior sections of the lophophore.
There is no apparent indication of the development of a dorsal median septum,
64
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
and it is certainly absent at a hinge width of about 8 mm. However, preservation
of brachial valves is not sufficiently good to be able to say with certainty that no
septum existed in old shells, especially as it is a structure which developed late in
the ontogeny of Rugosochonetes.
FIGS. 51-52. Illustrations of the pedicle valve interior of Rugosochonetes delicatus sp. n.
(Fig. 51) and R. silleesi sp. n. (Fig. 52) showing the difference in the internal spine
openings.
TABLE 25
I mm. (var.) = 5-26 (1-367)
w mm. (var.) = 7-63 (2-341)
r = 0-980
a (var.) = 1-309 (0-00404)
I mm. (var.) = 5-26 (1-367)
tn mm. (var.) = 1-58 (0-315)
r = 0-803
a (var.) = 0-480 (0-00481)
TABLE 25. Statistics of length (1), maximum width (w) and thickness (th) of 19
pedicle valves of Rugosochonetes delicatus sp. n.
TABLE 26
Ribs
6
7
8
9
at 2 mm.
4
9
3
3
at 4 mm.
4
8
7
i
TABLE 26. Number of ribs counted per mm. width at 2 mm. and 4 mm. antero-medianly
of the ventral umbo of R. delicatus sp. n.
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 65
Rugosochonetes transversalis sp. n.
(PI. 9, figs. 16-25)
DIAGNOSIS. Wide Rugosochonetes with semi-elliptical outline, low rounded
costellation; median ridges of cardinal process subparallel and narrowly separated;
socket ridges prominent and divergent from hinge-line.
DESCRIPTION. Outline transversely semi-elliptical, about one-half as long as
wide, umbo flattened, not extending beyond hinge-line which constitutes greatest
width of shell; profile concavo-convex, regular, about one-third as deep as long,
body cavity narrow, commonly slightly sulcate; hinge-spines irregularly placed at
high angle; multicostellate, ribs low rounded with rare apertures, costellae added by
dichotomy on both valves, with about 3 ribs occurring per mm. width, 4 mm.
antero-medianly from ventral umbo ; growth lines indistinct ; ventral interarea more
or less orthocline, delthyrium about one-third closed by highly arched apical pseudo-
deltidium; dorsal interarea orthocline to apsacline, about one-half length of ventral
interarea, notothyrium with U-shaped chilidium ; teeth diverging slightly from inter-
area; short high median septum separating elongate oval adductor scars, with
flanking trigonal diductor scars ; median ridge may extend anteriorly from septum for
2 or 3 mm. ; two low ridges extend beyond median ridge from anterior ends of
adductor scars for about two-thirds valve length (possibly traces of vascula media) ;
cardinal process rather wide, median muscle ridges narrowly separated, lateral
ridges divergent giving quadrified postero-dorsal surface; sockets deep, anteriorly
bordered by prominent socket ridges extending about one-quarter hinge width;
adult median septum partly fills alveolus, extending nearly one-half valve length,
broad and low, anteriorly raised; lateral septa diverge at 25° from mid-line, and
separate elongate oval anterior adductor scars from wider trigonal posterior scars ;
internally radially tuberculate except postero-laterally; shell substance pseudo-
punctate.
MEASUREMENTS (in mm.) :
length width
HOLOTYPE. Complete shell (66.52778) 13-5 c. 23-0
PARATYPES. Incomplete pedicle valve (66.52779) c. n-o c. 22-0
Incomplete pedicle valve (66.52781) 5-5
Complete brachial valve (66.52783) 10-0 19-5
TYPE LOCALITY. Sillees River, about 300 yds east of 6unnahone Lough (Low
D zone).
DISCUSSION. The radial ribbing is almost as wide as that found within Plico-
chonetes, as emended by Muir-Wood (1962 : 82), but differs in being poorly defined
with low indistinct ribs. 6ranching is not common but almost invariably by dicho-
tomy. Table 28 shows the distribution of costellation on pedicle valves. Growth
lines are indistinct and may be impossible to distinguish on the silicified material.
This poorly defined ornamentation cannot be attributed to abrasion, prior to silicifi-
cation, as delicate structures, such as hinge spines and the pseudodeltidium are
GEOL. 1 6, I. 5
66
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
preserved, and the concave brachial valves would have been well protected. About
one-half of the pedicle valves show sporadic concentric lamellae, probably indicating
some irregular retardations of growth. Eight out of twelve shells have a slight
median sulcation in their pedicle valves which dies out towards the anterior margin.
This folding is even less marked on the brachial valves. Currie (1937 : 423) pointed
out that a median sulcation of Chonetacea arose in the mid Carboniferous and it may
be that the slight sulcation seen on several of the Fermanagh shells is an indication
of this trend.
In outline R. transversalis is similar to C. laguessiana de Koninck mut. 6 Hind from
the Gin Mine Marine Band, N. Staffs. (Brit. Mus. (Nat. Hist.) 6.47309), but this shell
is more finely ribbed, and in this respect is comparable to R. celticus s.s. It has
about 8 spines in 10 mm. on either side of the umbo which contrasts with 5 or 6
spines in the same distance on the Fermanagh shells. In R. transversalis most of the
spines retain internal openings, the more medianly placed spines having oblique
canals leading to their openings which are lateral of the teeth. The internal surfaces
of the ears, and regions immediately anterior of the interareas, are not tuberculate,
but the ear regions are irregularly pitted. In old shells, the radial rows of tubercles
tend to coalesce into low ridges with the tips of the tubercles still protruding from
their crests. The ventral median septum terminates posteriorly in a thickened
region between the bases of the teeth and below the apex of the delthyrium, but with-
out the distinctly node-like callus of R. silleesi.
The dorsal median septum is typical for the genus in its late development, and the
lateral septa are again prominent anteriorly, protruding from the valve floor to the
inferred position of the body wall. Like the ventral valve, tuberculation is confined
to the mid and lateral regions, and towards the cardinal extremities the pair of slight
knobs probably assisted in the articulation of this long-hinged species. Brachial
ridges are not clearly distinguishable.
TABLE 27
1 mm. (var.) = 10-70 (9-6943) 1 mm. (var.) = 10-70 (9-694)
w mm. (var.) = 18-78 (40-640) fn mm. (var.) = 3-77 (4-257)
r = 0-578 r = 0-770
a (var.) = 2-048 (0-0465) a (var.) = 0-663 (0-0298)
TABLE 27. Statistics of length (1), maximum width (w) and thickness (th) of 8 shells
or pedicle valves of Rugosochonetes transversalis sp. n.
TABLE 28
Ribs
3
4
5
at 2 mm.
o
6
5
at 4 mm.
9
3
o
TABLE 28. Number of ribs counted in i mm. width at 2 and 4 mm. antero-medianly from
the pedicle umbo of Rugosochonetes transversalis sp. n.
SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH 67
Genus PLICOCHONETES Paeckelmann, 1930
TYPE SPECIES. Chonetes buchianus de Koninck, 1843, by original designation
of Paeckelmann (1930 : 222).
Plicochonetes buchianus (de Konick)
(PL 9, figs. 27-32)
DIAGNOSIS (emended). Strong concavo-convex Plicochonetes with narrow body
cavity; prominent rounded ribs, not developed postero-laterally; small pseudo-
deltidium and chilidial plates present ; dorsal median septum short and low.
DESCRIPTION. Outline subsemicircular with straight hinge-line at widest part
of shell, about two-thirds as long as wide; ears well developed and smooth; profile
concavo-convex with narrow body cavity, shell about one-half as deep as long;
radial ornament prominent and evenly developed from about 16 costae with rare
additions of ribs by branching on pedicle valves and intercalation on brachial valves,
about 5 ribs per 2-5 mm. at 4 mm. from ventral umbo, rib-apertures sparsely
developed on both valves; growth lines finely developed; ventral interarea concave,
more or less orthocline, delthyrium closed apically by small arched pseudodeltidium ;
at least seven pairs of hinge spines subparallel to mid-line; dorsal interarea hyper-
cline with notothyrium similarly sized to delthyrium and flanked by prominent
chilidial plates; teeth suboval in outline; short high median septum extending as
low ridge between elongately oval adductor scars ; diductor scars poorly impressed ;
cardinal process bilobed and medianly fused, external face quadrifid with prominent
median muscle boundaries separated by narrow groove; socket ridges extending
about one-third hinge-line width; median septum low and broad, raised anteriorly
and extending about one-quarter valve length, but continued as short ridge; lateral
septa at 25° to 30° from mid-line, commonly prominent anteriorly; brachial im-
pressions lobate, extending about three-fifths valve length and disc width; shell
substance thin.
MEASUREMENTS (in mm.) :
length width
Complete shell (66.52917) 7-8 12-8
Incomplete brachial valve (66.52918) 10-6 c. 16-0
Incomplete brachial valve (66.52919) 6-9
DISCUSSION. The species is rarely found in the limestones from Co. Fermanagh,
but a few well preserved specimens warrant discussion.
The genus was inadequately described by Paeckelmann (1930). In her description
of the genus Muir-Wood (1962 : 82) makes no mention of the presence of chilidial
plates. These are well developed arching the lateral flanks of the external face of the
cardinal process so as partially to obscure the lateral muscle boundary ridges (PI. 9,
fig. 30). The plates are barely fused medianly, but were well developed when the
68 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
valve was 6 mm. long. The presence of a well defined apical pseudodeltidium in the
present material indicates that this structure may be commoner on well preserved
material than has been thought. This structure, together with the chilidial plates
should be noted within a diagnosis of Plicochonetes.
The correspondence between the ribbing of the brachial and pedicle valves is in-
dicated by the way in which costellae are commonly added by intercalation on the
brachial valve in a position opposite to a branched rib on the pedicle valve. An
example of this can be seen on the shell illustrated on PL 9, figs. 29, 30. This is
considered to be a common feature of ribbing, and is a necessity for a close fit of the
anterior margin, but is difficult to demonstrate on more finely ribbed groups.
Rib apertures are developed both on the ribs and sparsely on the smooth ears
in a radial fashion. These structures are more fully discussed under Rugosochonetes.
In common with other chonetaceids, the lateral septa developed at an early stage,
prior to the differentiation of the median septum or clear development of the
adductor scars (PI. 9, fig. 31). Their prominence indicates a functional importance
and their prolonged anterior extremities probably assisted in the support of the
lophophore at the body wall as in Rugosochonetes.
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70 SILICIFIED BRACHIOPODS FROM COUNTY FERMANAGH
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EXPLANATION OF PLATES
Unless otherwise stated, all the specimens are housed in the British Museum
(Nat. Hist.); were collected from the silicified limestone of Co. Fermanagh, and have
been sprayed with ammonium chloride immediately prior to being photographed.
PLATE I
Crania quadrat a (M'Coy)
FIGS, i, 2. External and internal views of broken brachial valve. 66.55599. Xi-5-
FIG. 3. External view of brachial valve. 66.55601. X4-o.
FIGS. 4, 5. External and internal views of brachial valve. 66.55600. X2-i.
FIGS. 6, 7. Dorsal and lateral views of brachial valve. 66.55616. x6-2.
FIG. 8. External view of brachial valve. 66.55602. X5-8.
FIG. 9. External view of brachial valve. 66.55603. x 5-2.
Acanthocrania cf. laevis (Keyes)
FIG. 10. External view of brachial valve. 66.55605. X3'i.
FIG. ii. External view of fragment of brachial valve. 66.55606. x 2-9.
FIGS. 12-14. Lateral, dorsal and internal views of brachial valve. 66.55604. x 3-0.
Philhedra trigonalis (M'Coy)
FIGS. 15, 1 6. Dorsal and lateral view of brachial valve attached to a rugosochoneteid
66. 55607. x 2-0.
FIGS. 17, 18. Lateral and dorsal views of brachial valve. 66.55608. X2-o.
FIGS. 19-21. Lateral, internal (X2-5) and dorsal views of brachial valve. 66.55610.
X2-0.
FIGS. 22, 23. Internal and lateral views of brachial valve. 66.55609. x 2-0.
FIGS. 24-26. Internal, dorsal and lateral views of brachial valve. 66.55611. x 2-0.
FIGS. 27-29. Lateral, dorsal and internal views of brachial valve with a small portion of the
pedicle valve still attached. 66.55612. X2'O, X 2-3 and x 3 -5 respectively.
FIGS. 30, 31. Internal and external views of brachial valve. 66.55614. X5'2.
FIGS. 32, 33. Dorsal and lateral views of brachial valve. 66.55613, x 3-0.
Bull. Br. Mus. nat. Hist. (Geol.) 16, i
PLATE i
GEOL. 1 6, I
PLATE 2
Schizophoria resupinata (Martin)
FIGS. 1-3. Neotype, from Bolland (Gilbertson Colin.) viewed dorsally, ventrally and an-
teriorly. BB.2420. x 0-5.
FIGS. 4, 5. Part of brachial valve from the Visean of Cam Back, Yorks., viewed externally
( x 0-5) and internally ( x 0-95) . 6.56088.
FIG. 6. Part of brachial valve from the Visean of Ulverstone, Lanes., showing the trilobed
cardinal process and fulcral plates. 30113. Xo-95.
Schizophoria resupinata dorsosinuata Demanet
FIGS. 7-11. Incomplete shell viewed dorsally, ventrally, laterally, posteriorly and anteriorly.
BB. 52701. xi-6.
FIGS. 12, 13. Incomplete shell viewed postero-ventrally and dorsally. 66.52702. xi-6.
FIG. 14. Incomplete brachial valve cardinalia. 66.52710. x 2-7.
FIGS. 15, 16. Incomplete pedicle valve viewed posteriorly and dorsally. 66.52704. X2-3.
FIG. 17. Cardinalia of brachial valve. 66.52705. X4-o.
FIG. 18. Ventral view of incomplete young brachial valve. 66.52712. x 3-3.
FIG. 19. Ventral view of incomplete young brachial valve. 66.52706. x 6-0.
FIG. 20. Incomplete brachial valve interior. 66.52922. X5-o.
FIG. 21. Incomplete brachial valve interior. 66.52933. x 2-0.
FIGS. 22-25. Young shell viewed posteriorly, anteriorly, dorsally and ventrally. 66.52716.
x6-o.
FIGS. 26, 27. Young pedicle valve interior and exterior. 66.52714. x 3-1.
FIGS. 28, 29. Young brachial valve exterior and interior. 66.52708. x 6-0.
FIG. 30. Juvenile brachial valve interior. 66.52707. X 6-0.
FIGS. 31, 32. Juvenile pedicle valve exterior (x6>5) and interior (x8~5) 66.52713.
FIGS. 33-36. Juvenile shell viewed ventrally, dorsally, anteriorly and posteriorly. 66.52717
x8-75.
FIG. 37. Incomplete brachial valve interior. 66.52715. X 2-3.
Bull. Br. Mus. nat. Hist. (Geol.) 16, i
PLATE 2
GEOL. 1 6, I
6§
PLATE 3
Rhipidomella michelini (L'Eveill6)
FIGS. 1-3. Complete topotypic shell from Tournai, Belgium, viewed ventrally, dorsally
and posteriorly. 36.55617 (reregd. from 6.18254). X i-i.
FIGS. 4, 5. Brachial valve, from Tournai, Belgium, viewed antero-ventrally and ventrally.
66.55618. xi-i.
FIG. 6. Pedicle valve interior, from Tournai, Belgium, 66.55619. Xi-i.
FIGS. 7-10. Complete shell viewed dorsally, ventrally, laterally and posteriorly. 66.52718.
X2-4.
FIGS, n, 12. Incomplete pedicle valve viewed dorso-laterally and dorsally. 66.52719.
X3-5-
FIGS. 13, 14. Posterior portion of shell viewed internally and externally. 66.52727.
X4'5-
FIGS. 15-18. 6rachial valve exterior, interior (X2-87), posterior (X3-8) and lateral (X2-8)
views. 66.52722.
FIGS. 19, 20. Pedicle valve exterior (X2-5) and interior (X3-o) 66.52720.
FIGS. 21, 22. Juvenile shell viewed dorsally and ventrally. 66.52724. x 3-8.
FIG. 23. Incomplete brachial valve cardinalia. 66.52728. x 3-5.
FIGS. 24, 25. Juvenile brachial valve exterior and interior. 66.52726. X4*5.
Leptagonia analogia (Phillips)
FIGS. 26, 27. Lectotype from the lower Carboniferous of 6olland, in the Gilbertson Colin,
viewed dorsally and ventrally. 6.8936. Xi-o.
FIG. 28. Incomplete pedicle valve interior, from the lower Carboniferous Redesdale
limestone, Northumberland. 66.46524. x 3-0.
FIGS. 29, 30. Internal mould, retaining fragments of shell, viewed anteriorly and dorsally,
from the Gilbertson Colin. 66.55777. X i-o.
FIG. 31. Complete shell from the Lower Carboniferous of Carrick-on-Shannon, Eire, viewed
ventrally. Hunterian Museum L. 38 17/1. x i-o.
Bull. Br. Mus. nat. Hist. (Geol.) 16, i
PLATE 3
31
PLATE 4
Leptagonia analoga (Phillips)
FIG. i. Brachial valve cardinalia from Carrick-on-Shannon. Hunterian Mus., L.3834/22.
X3-o.
FIG. 2. Brachial valve interior from Redesdale, Northumberland showing a mature cardina-
lia and saccate pallial sinuses. 6.43708. Xi -i.
FIG. 3. Incomplete silicified brachial valve exterior. 66.52921. X3'4.
FIGS. 4, 5. Juvenile shell viewed dorsally (x 5-0) and ventrally (x 3-4). 66.52729.
FIGS. 6, 7. Juvenile brachial valve interior and exterior. 66.52730. x 5-0.
FIGS. 8, 9. Incomplete brachial valve from the Lower Carboniferous of Co. Sligo viewed
posteriorly (Xi'3) and ventrally (xo-g). 66.52731.
Derbyoides nebrascensis Dunbar & Condra
FIGS. 10-12. Topotypic incomplete pedicle valve from the Upper Carboniferous near
Nehawka, Nebraska, viewed externally, anterodorsally and dorsally. 66.55491. x i-o.
FIGS. 13, 14. Topotypic incomplete brachial valve exterior and interior. 66.55490. X i -o.
Tapajotia tapojotensis (Derby)
FIGS. 15, 16. Topotypic incomplete pedicle valve from the Upper Carboniferous of Rio
Tapajos, 6razil, viewed dorsally and anterodorsally. 66.55493. x i-o.
FIGS. 17-19. Topotypic young pedicle valve viewed antero-dorsally, dorsally and ventrally.
66.55496. X2-i.
FIGS. 20, 21. Topotypic incomplete brachial valve viewed posteriorly and ventrally.
66.55494. xi-5.
FIGS. 22, 23. Topotypic young brachial valve exterior and interior. 66.55495. X2-I.
Brochocarina wexfordensis (Smyth)
FIG. 24. Paratype. Incomplete pedicle valve interior from Hook Head, Co. Wexford.
Trinity College Dublin Colin. Xo-75.
FIGS. 25, 26. Holotype. 6rachial valve viewed posteriorly (Xi'3) and externally (xo-7).
Trinity College Dublin Colin.
Bull. Br, Mus. nat. Hist. (Geol.) 16, i
PLATE 4
26
PLATE 5
Brochocarina wexfordensis (Smyth)
FIGS. I, 2. Incomplete pedicle valve exterior and interior. 66.55779. x i-o.
FIGS. 3, 4. Pedicle valve exterior and interior. 66.55598. Xo«75.
FIG. 5. Incomplete pedicle valve interior. 66.55778. X i-o.
FIG. 6. Incomplete shell viewed postero-dorsally. 66.55597. x 1-5.
FIG. 7. Incomplete pedicle valve interior. 66.52733. x 1-7.
FIG. 8. Juvenile pedicle valve interior. 66.52734. X 2-7.
FIGS. 9, 10. Juvenile brachial valve exterior and interior. 66.55596. x 2-0.
FIGS. 11-13. Incomplete pedicle valve exterior (xo-8) detail of external ornamentation
(X3-o) and interior (xo-8). 66.52732.
FIGS. 16, 17. Adult cardinalia viewed ventrally and posteriorly. 66.55595. X3-o.
FIG. 18. Partially crushed shell from 6undoran, Co. Donegal, showing posterior view of
cardinal process and chilidium. 66.52738. x 1-8 (not silicified).
FIG. 19. Incomplete shell from Poll More, near 6oho, Co. Fermanagh, showing the ventral
interarea. 66.52737. x 1-6 (not silicified).
FIGS. 20, 21. Juvenile brachial valve interior and exteroir. 66.55594. X4-o.
FIGS. 22, 23. Juvenile brachial valve interior and exterior. 66.55593. X3-o.
Bull. BY. Mus. nat. Hist. (Geol.) 16, i
PLATE 5
18
PLATE 6
Serratocrista fist ulosa sp. n.
FIGS. 1-3. Holotype. Complete shell viewed dorsally and ventrally (xi-8) and detail of
external ornamentation (x6-o). BB. 52739.
FIG. 4. Pedicle valve interior. 66.52741. Xi-6.
FIG. 5. Incomplete brachial valve interior. 66.52743. xi-7-
FIG. 6. Young brachial valve interior. 66.52740. x 1-8.
FIG. 7. Juvenile pedicle valve exterior. 66.52744. x 4-4.
FIG. 8. Incomplete pedicle valve interior. 66.52742. x 1-7.
FIGS. 9, 10. Incomplete brachial valve exterior and interior. 66.55488. x 2-2.
FIGS, ii, 12. Fragment of pedicle valve viewed laterally and dorsally. 66.55489. X2-2.
Schellwienella radialis (Phillips)
FIGS. 13-16. 6rachial valve viewed externally, internally and laterally (x 1-3) and detail of
the external ornamentation (X2-3). 66.52747.
FIG. 17. Incomplete pedicle valve viewed antero-dorsally. 66.52745. x 3-2.
FIG. 1 8. Juvenile brachial valve interior. 66.52746. x 2-6.
FIG. 19. Detail of external ornamentation on a crushed, unsilicified specimen from 6ohenvy,
about i£ miles north of the Sillees R. locality. 66.52750. X2-4.
FIG. 20, 21. 6rachial valve viewed posteriorly and ventrally. 66.52748. x 1-6.
FIGS. 22, 23. 6rachial valve cardinalia from 6ohenvy, internally (xi-i) and externally
(Xi'7). 66.52749 (unsilicified).
FIG. 24. Holotype. 6rachial valve exterior, collected from Florence Court, Co. Fermanagh.
The University Museum, Oxford. £.2054. x i-o.
Bull. Br. Mus. nat. Hist. (Geol.) 16, i
PLATE 6
21
PLATE 7
Orthotetinid gen. et. sp. indet.
FIGS. I, 2. Juvenile incomplete brachial valve exterior and interior. 66.55782. x 1-9.
FIGS. 3, 4. Incomplete brachial valve exterior and internal view of cardinalia. 63.55780.
Xi-o.
FIGS. 5-7. Dorsal cardinalia viewed dorsally, ventrally and posteriorly showing the com-
plete chilidium. 66.55781. + 1-0.
Globosochonetes parseptus sp. n.
FIGS. 8-1 1 . Complete shell viewed dorsally, ventrally, posteriorly and anteriorly. 66.55498.
X5'7-
FIGS. 12-14. Complete pedicle valve viewed externally, dorsally and antero-dorsally to show
the short median septum. 66.52752. x 7-5.
FIGS. 15-18. Holotype. Complete, disarticulated shell viewed posteriorly, dorsally, ven-
trally and laterally. 66.52751. X7'5-
FIGS. 19, 20. Incomplete shell viewed ventrally and dorsally. 66.55783. x 6-4.
FIG. 21. Incomplete adult brachial valve interior showing short median septum. 66.52754.
X7'7-
FIG. 22. Incomplete brachial valve interior. 66.52753. x 7-5.
FIG. 23. Juvenile pedicle valve viewed posteriorly to show pedicle sheath. 66.52757.
Xio-i.
FIG. 24. Young pedicle valve viewed posteriorly to show pedicle sheath. 66.52756,.
X7-5-
FIG. 25. Juvenile brachial valve interior. 66.52755. xii-5-
FIGS. 26, 27. Young brachial valve with damaged accessory septum, interior and exterior.
B6.55499. X5«5.
Rugosochonetes celticus Muir-Wood
FIGS. 28, 30. Holotype. Complete shell from the Visean of Flint, N. Wales, viewed ventrally,
anteriorly, posteriorly and dorsally. 66.41145. X2-o.
Bull. Br. Mus. nat. Hist. (Geol.) 16, i
PLATE 7
PLATE 8
Rugosochonetes celticus Muir-Wood
FIG. i. Complete shell viewed ventrally, identical to holotype and collected from the Lower
Carboniferous of Cam Beck, Yorkshire. 3.48887. x 2-0.
FIGS. 2, 3. Complete pedicle valve exterior and interior, also from Cam Beck, but of the
coarsely ribbed group. 6.48894. X2-o.
FIGS. 4, 5. Pedicle valve interior and exterior of coarsely ribbed specimen from the Visean
of Beith, Ayrshire. 8.53892. x 2-0.
FIGS. 6, 7. Dorsal and ventral views of poorly ribbed specimen from the Visean of Ancroft,
Northumberland. 66.42045. X2-o.
FIGS. 8, 9. Ventral and dorsal view of similar specimen from Aycroft. 66.42046. X 2-0.
Rugosochonetes silleesi sp. n.
FIGS. 10-13. Holotype. Complete shell viewed dorsally, ventrally, posteriorly and laterally.
66.52758. xi-7.
FIGS. 14, 15. Complete brachial valve exterior and interior. 66.52761. X2-4.
FIG. 1 6. Incomplete brachial valve interior. 66.52762. X2-9.
FIGS. 17, 1 8. Pedicle valve viewed antero-dorsally and dorsally. 66.52759. X2'7.
FIG. 19. Incomplete shell viewed dorsally. 66.52770. X5-o.
FIG. 20. Juvenile brachial valve interior. 66.52763. x 7-5.
FIG. 21. Young pedicle valve interior. 66.52765. X3'O.
FIG. 22. Pedicle valve interior viewed anteriorly. 66.52760. x 2-7.
FIGS. 23, 24. Incomplete brachial valve viewed postero-ventrally and postero-dorsally.
66.52764. X3-0.
FIG. 25. Shell viewed postero-dorsally. 66.52766. X 2-7.
FIG. 26. Juvenile pedicle valve exterior showing pedicle sheath. 66.52768. x 7-5.
FIG. 27. Young pedicle valve interior. 66.52767. X4-I.
Bull. Br. Mus. nat. Hist. (Geol.) 16, i
PLATE 8
PLATE 9
Rugosochonetes silleesi sp. n.
FIGS. 1,2. Two unsilicified slightly crushed shells from the shale below the silicified limestone
at the Sillees river to show shell ornamentation. 63.52769. (x^'75), 66.55784 (X2-4)
respectively.
Rugosochonetes delicatus sp. n.
FIGS. 3-5. Holotype. Incomplete shell viewed ventrally, dorsally and laterally. 66.52771.
X375- \
FIGS. 6, 7. Complete shell viewed dorsally and ventrally 66.52774. x 3-8.
FIGS. 8-1 o. Incomplete pedicle valve viewed ventrally, anteriorly and posteriorly.
66.52773. X3-75.
Fig. ii. Pedicle valve exterior. 66.52775. X3-75.
Figs. 12, 13. Pedicle valve viewed antero-dorsally and dorsally. 66.52772. X3-7-
Fig. 14. Crushed juvenile shell with pedicle sheath, viewed ventrally. 66.52776. X3-75-
Fig. 15. Incomplete brachial valve interior. 66.52777. x 5.0.
Rugosochonetes transversalis sp. n.
Fig. 16. Fragment of brachial valve interior. 66.52784. x 2.7.
Figs. 17, 18. Incomplete pedicle valve viewed anteriorly and dorsally. 66.52779. x 1.7.
Figs. 19-22. Holotype. Incomplete shell viewed posteriorly dorsally, ventrally and later-
ally. 66.52778. Xi. 6.
FIG. 23. 6rachial valve interior. 66.52783. Xi-7.
FIGS. 24, 25. Dorsal cardinalia viewed ventrally and posteriorly. 66.52785. X2.75.
FIG. 26. Incomplete young pedicle valve interior. 66.52781. X2.75.
Plicochonetes buchianus (de Koninck)
FIGS. 27-30. Shell viewed ventrally, laterally, postero-ventrally and dorsally. 66.52917.
X2.4.
FIG. 31. Incomplete juvenile brachial valve interior. 66.52919. X2.4.
FIG. 32. Incomplete valve interior. 66.52918. X2-4-
Bull. Br. Mus. nat Hist, (Geol.) 16, i
^^^ill
32
PRINTED IN GREAT BRITAIN
BY ADLARD & SON LIMITED
BARTHOLOMEW PRESS, DORKING
S-H.
A REVISION OF THE FORAMINIFE
GENUS AUSTROTRILLINA PARR
cN2
C. G. ADAMS
BULLETIN OF
THE BRITISH MUSEUM (NATURAL HISTORY)
GEOLOGY Vol. 16 No. 2
LONDON: 1968
A REVISION OF THE FORAMINIFERAL GENUS [ -SFEB
AUSTROTRILLINA PARR
BY
C. G. ADAMS
British Museum (Natural History
Pp. 71-97; 6 Plates; 3 Text-figures
BULLETIN OF
THE BRITISH MUSEUM (NATURAL HISTORY)
GEOLOGY Vol. 16 No. 2
LONDON: 1968
THE BULLETIN OF THE BRITISH MUSEUM
(NATURAL HISTORY), instituted in 1949, is
issued in five series corresponding to the Departments
of the Museum, and an Historical series.
Parts will appear at irregular intervals as they become
ready. Volumes will contain about three or four
hundred pages, and will not necessarily be completed
within one calendar year.
In 1965 a separate supplementary series of longer
Papers was instituted, numbered serially for each
Department.
This paper is Vol. 16, No. 2 of the Geological
(Palaeontological) series. The abbreviated titles of
periodicals cited follow those of the World List of
Scientific Periodicals.
World List abbreviation
Bull. Br. Mus. nat. Hist. (Geol.).
Trustees of the British Museum (Natural History) 1968
TRUSTEES OF
THE BRITISH MUSEUM (NATURAL HISTORY)
Issued 6 February, 1968 Price £i I2s.
A REVISION OF THE FORAMINIFERAL GENUS
AUSTROTRILLINA PARR
By C. G. ADAMS
MS accepted May i2th 1967
ABSTRACT
The known species of Austrotrillina are redescribed and compared, and their
geographical and stratigraphical distributions are discussed. It is concluded that
the evolutionary changes observed in the wall structure are of value in stratigraphy.
One new species, A . asmariensis, is erected.
CONTENTS
I. INTRODUCTION ......... 73
II. STRATIGRAPHICAL NOTES ....... 75
III. SYSTEMATIC PALAEONTOLOGY ...... 80
(a) Shell structure ....... 80
(b) Description of species ...... 82
(c) Outstanding problems ...... 93
IV. CONCLUSIONS ......... 93
V. REFERENCES ......... 95
I. INTRODUCTION
Austrotrillina has long been recognized as an important mid-Tertiary index fossil
in the Tethyan and Indo-Pacific regions. It is unknown from the Americas. Un-
fortunately, the four species so far described, A. howchini (Schlumberger) , A.
paucialveolata Grimsdale, A . brunni Marie, and A . striata Todd & Post, have never
been adequately compared, their diagnostic characters have hitherto been uncertain
and the stratigraphical value of the individual species has therefore been obscured.
The purpose of this paper is to redescribe these species, to establish the facts about
their geographical and stratigraphical distributions as accurately as possible, and to
indicate the probable evolutionary history of the genus.
Since Austrotrillina occurs in both the Tethyan and Indo-Pacific provinces, it is
necessary to refer here to two schemes of classification for the Tertiary (Text-fig, i).
Justification for the correlation between part of the East Indian letter stages (Tc-Te)
and the European stages may be found in a recent paper (Adams 1965). It is
thought wise to retain the two systems until a generally acceptable correlation
becomes possible.
GEOL. 1 6, 2 7
74
A REVISION OF AUSTROTRILLIN A
o
«/> -—
Approximate
Ifl
0)
c U
> c
<l>
c o rrelat ion
u
"I O O _C
wi th
Q.
O ,j n <-*
CO
^ o o 2
u ro pean
o a w) JE
- r^
< < < <
c <
stages
Ag e
Age
Q}
Upper
i—
z
Tf
"^ U
()
u O
p
(Tf3)
^^
y
Lower
CO
Tf
Burd igalian
<D
CO
(Tfl-2)
C
tt
(J
Upper
^
1
0
CtL
Te
^
LU
(Te5)
1
Aq ui t a n ia n
0)
LU
—1
Lower
1
0
Te
Z
[Te ]_ 4)
1
Chat t ia n
Q
1
Z
tt
—
Td
R u p e 1 i a n
c
0)
1
u
CO
i
o
11 1
i
-
0
Tc
"Lattorf ian"
A REVISION OF AUSTROTRILLINA 75
It was first realized that taxonomic confusion surrounded the species of Austro-
trillina during a study of the Tertiary faunas of Borneo. At the same time it be-
came clear that the genus showed definite evolutionary changes during the Miocene
and that if these could be shown to hold good over the whole of its distributional area,
a useful stratigraphical tool would have emerged.
Although well-placed to attempt this study, the writer would have achieved little
without the willing co-operation of numerous fellow workers. His special thanks are
due to the following: Dr. F. E. Eames (British Petroleum Co. Ltd.) for stimulating
discussions, for help in obtaining material from Iran and Malta and for critically
reading the manuscript; Dr. T. D. Adams and Mr. J. D. Baignton (Iranian Oil
Operating Co.) for additional material from Iran and for much useful stratigraphical
data; Dr. R. C. van Bellen and Mr. G. F. Elliott (Iraq Petroleum Co. Ltd.) for the
loan of material and for valuable stratigraphical evidence; Dr. N. H. Ludbrook
(Department of Mines, Adelaide) for the gift of specimens from the Pata limestone,
South Australia, and for much helpful information; Dr. R. Cifelli (U.S. National
Museum), Miss Ruth Todd and Dr. N. K. Sachs (U.S. Geological Survey) for making
available material in their care. He is also greatly indebted to Dr. F. T. Banner
(British Petroleum Company Ltd.), Dr. D. J. Belford (Bureau of Mineral Resources,
Canberra), Dr. A. N. Carter (University of New South Wales), Mr. D. J. Carter (Im-
perial College, London), Professor W. Storrs Cole (Cornell University), Professor
M. F. Glaessner (University of Adelaide), Dr. L. Hottinger (University of Basle) and
Dr. P. Marie (Paris) for additional information, material, or helpful discussions,
Mr. R. L. Hodgkinson provided invaluable technical assistance.
II. STRATIGRAPHICAL NOTES
The species described here were obtained mainly from the successions detailed be-
low. This stratigraphical information is given so that the conclusions regarding
stratigraphical ranges and evolutionary history can be evaluated independently
by other workers.
i. The Asmari limestone
General succession Age (according to Eames et al. 1962)
Upper Asmari limestone Burdigalian
Middle Asmari limestone Aquitanian
f upper part Chattian
Lower Asmari limestone Ohgocene«c , , -^ v
flower part Rupehan
The Asmari limestone overlies the Brissopsis beds (Lower Oligocene) in some
places; in others it rests disconformably on the Upper Eocene.
Whether or not the middle Asmari limestone is Aquitanian in age seems to be a
matter of opinion. Direct correlation with the type Aquitanian is impossible at
present, and the published evidence does not appear to disprove an Upper Oligocene
age for this part of the sequence.
76 A REVISION OF AUSTROTRILLIN A
Material examined in this study consists of :
(a) 2,500 thin sections from wells 6 and n, Gach Saran Oilfield, Iran. Both
wells penetrated all three divisions of the limestone.
(b) The Asmari limestone at Kuh e Pataq, N.W. Luristan (46° oo' E., 34° 25' N.).
Four samples were available from this locality, here designated as the type section for
A. asmariensis sp. nov. The microfauna of the whole section has been studied by
Dr. T. D. Adams and the ranges of important genera shown on Text-fig. 2 are based
on his work. Kuh e Pataq is a surface section on the road from Kermanshah to
Baghdad, near the border with Iraq (Text-fig. 2). The lowermost part of this
sequence is definitely Eocene, and although it is tempting to regard the oldest
Oligocene horizons as Lower Oligocene (occurrence of Nummulites fichteli without
Eulepidina) caution is necessary. Eulepidina does not appear until 380 ft. below
the top of the limestone and the overlap with N. fichteli is small (about Soft.).
Reticulate nummulites occur through approximately 700 ft. of limestone and overlap
with Chapmanina (a well-known Eocene genus) throughout their lowermost 130 ft.
The writer has not seen these particular specimens and is therefore unable to con-
firm Dr. T. D. Adams's identification of N. fichteli (in lit.}. It seems reasonable to
draw the Eocene /Oligocene boundary at about 845 ft. below the top of the limestone,
i.e. at the first appearance of Austrotrillina. It may be noted that Austrotrillina
is not common until after the incoming of Peneroplis thomasi about 800 ft. from the
top. By 730 ft. P. thomasi has already been joined by P. evolutus and Praerhapy-
dionina delicata. The evidence of this section seems to suggest that Austrotrillina
occurs in the Lower Oligocene. However, it can equally well be argued that this is a
Middle Oligocene fauna from which Eulepidina is absent for facies reasons. Pending
further investigation of the section — in particular, the detailed examination of the
faunas immediately above the Eocene /Oligocene boundary — it would be unjustifi-
able to state unequivocally that Austrotrillina occurs in the Lower Oligocene of
Kuh e Pataq, although it certainly occurs in the Middle Oligocene.
(c) The Kuh e Kalagh section (Text-fig. 2). The lowest exposed Oligocene beds
in this locality are presumably of Middle Oligocene age (association of Lepido-
cyclina, in part Eulepidina, with Nummulites fichteli}. The base of the Oligocene is
obscured and the next visible beds are those of the Eocene Dezak Marl Member.
The middle part of the section is either Chattian or Aquitanian but seems to lack
diagnostic fossils; the highest levels (above sample JHT 1863 and not shown in
Text-fig. 2) can reasonably be assigned to the late Lower Miocene (" Burdigalian ")
on the evidence of Borelis melo curdica. Ninety- two samples (135 thin sections),
collected through 1,138 ft. of rock, have been examined.
2. The Main Limestone of Kirkuk.
This limestone is well-known through the work of van Bellen (1956). It has been
described from numerous wells which are difficult to correlate owing to the rapidity
with which it is said to changes facies both laterally and vertically. The succession
A REVISION OF AUSTROTRILLIN A
77
KUH E PATAQ
Centre - North East Flank
G. S.
800'
-•1300'
Basal occurrence of
Lepidocyclina JTP
4917
[01 p| Conglomerate
O Obscured
Vertical Scale: 2cmi
100 ft.
KUH E KALAGH
West
J H T 1981 - «=rS=^=ri -
'», KUH-E-PATAQ
KERMANSHAH
IRAN
'ASMARI
I RAO
50°
FIG. 2. Two surface sections of the Asmari limestone. Kuh e Pataq is the type locality
for A. asmariensis sp. nov. Data kindly provided by Dr. T. D. Adams (Iranian Oil
Operating Companies). For Borelis pygmaea read Borelis pygmaeus.
78 A REVISION OF AUSTROTRILLIN A
in Well K.I4, from which A. paucialveolata was first described, is as follows:
Succession Age
Lower Fars conglomerate Burdigalian
— disconformity —
Baba Formation Middle Oligocene (on the association
(Thickness about 30 ft.) of Nummulites and Eulepidina).
(65 ft. in KIOQ, van Bellen p. 260) Fore-reef.
— disconformity
Shurau Formation High Lower Oligocene or Middle
(Thickness about 30 ft.) Oligocene. Types of A. pauci-
(60 ft. in type section, Kiog; alveolata from here. Back reef.
van Bellen p. 260)
Sheikh Alas Formation Lower Oligocene. N. fichteli
(85 ft. type section ; without Eulepidina. Fore reef.
van Bellen p. 260)
The Bajawan Formation, not represented in Well Ki/j., has as its type locality
Well Kiog (Baba Dome) where, according to van Bellen, it overlies the Baba lime-
stone conformably, has a thickness of 128 ft. and is developed in " back reef "
facies. According to Smout & Eames (1958) the Bajawan Formation is probably
Aquitanian in age, but the evidence for this is rather tenuous since it depends
largely on the assumption that Spiroclypeus does not occur in the Oligocene. It may
be noted that van Bellen (1956 : 260) said that the Baba Formation is the fore-
reef equivalent of the Bajawan limestone, in which case both are of Middle Oligocene
age. On the other hand, van Bellen had not seen Spiroclypeus in the Bajawan Form-
ation whereas Smout and Eames had.
3. Pemba Island
This sequence was described by Stockley (1927). Morley Davies, who described
the Foraminifera in the same publication, recognized the following subdivisions of
the Chake-Chake beds which are 100 ft. thick at outcrop.
Upper horizon Miogypsina without Lepidocyclina
Middle horizon (Datum Stratum) Amphistegina and Operculina
Lower horizon Lepidocyclina with very rare
Miogypsina
A. howchini was said by Morley Davies to range from " low down to high up "
in the Chake-Chake beds. He dated the entire sequence as high Aquitanian or
Burdigalian. These beds are here regarded as Lower Tf for reasons which are given
later (see p. 88).
4. The Kirimalai limestone, Ceylon
This limestone occurs in the northern part of the island on the Jaffna Peninsula.
An account of the stratigraphical succession and of the faunas of the Miocene lime-
A REVISION OF AUSTROTRILLIN A 79
stones of Ceylon was given by Wayland & Morley Da vies (1923). According to these
authors, the forminiferal fauna includes Orbiculina malabarica (= Taberina mala-
barica}, Sorites sp., Alveolinella (Flosculinelld) sp. and Spiroclypeus~? sp. cf. pleuro-
centralis, together with miliolids of various types. They also report the association
of Orbiculina sp. and Spiroclypeus orbitoideus from Minihagalkanda in the south of
the island. However, it is not clear whether these species were found in a single
sample or whether they occurred at different levels. A. howchini and Taberina
malabarica have been observed together in a thin section of limestone B.M.(N.H.)
P22330 from the Wayland collection labelled " North of Pomparippu, N.W.
Province, Ceylon."
5. The Melinau limestone, Sarawak
The general succession at Melinau is as follows :
Upper Te limestone 1,600 ft.
Lower Te limestone 1,600 ft.
Td limestone no ft.
Tc limestone 1,400 ft.
Tb limestone 1,850 ft.
Austrotrillina occurs from highest Td through Te. For full details of this lime-
stone see Adams (1965).
6. The Pata limestone, South Australia
This is the youngest Miocene limestone in the Murray Basin, and Ludbrook (1961)
has given details of its foraminiferal fauna. She referred it to the highest Burdi-
galian but, according to Eames et al. (1962), its pelagic foraminifera indicate a
Lower Burdigalian age. The position of the Pata limestone in terms of the East
Indian letter classification is Lower Tf.
7. The Miocene limestones of Saipan
Cole (1957) and Hanzawa (1957) have described the foraminifera from large
numbers of surface samples collected over the whole island. The geology has been
described by Cloud et al. (1956). Unfortunately, no good sections were measured
and the relative stratigraphical positions of many samples are uncertain from the
field evidence. It has been possible to examine the specimens described by Cole
(1957) in Washington and Ithaca, and matrix-free individuals have been extracted
from two important samples.
8. The Miocene limestones of Bikini and Eniwetok
The faunas of these limestones are known only from boreholes, and have been
described by Cole (1954; 1958), Todd & Post (1954) and Todd & Low (1960). The
types of A . striata come from bore 2B on Bikini Island. All the specimens of Austro-
trillina recovered from these bores have been examined through the courtesy of
Miss Ruth Todd and Professor W. Storrs Cole.
8o A REVISION OF AUSTROTRILLIN A
9. The Lower Coralline limestone of Malta
This limestone is at least 626 ft. thick (House et al., in Bowen- Jones 1961) and is
the oldest described rock unit on the island. However, unpublished information
(Eames in. lit.} shows that this unit is underlain by a miliolid limestone, at least
75 ft. thick, which lacks Austrotrillina. The lower Coralline limestone contains,
in addition to Austrotrillina, Peneroplis evolutus, Praerhapydionina delicata, Spiro-
clypeus blanckenhorni var. ornata, Lepidocyclina (Eulepidina} dilatata, Lepidocyclina
(N ephrolepidina} tournoueri and Miogypsinoides complanatus. On the basis of this
assemblage it has been dated as Aquitanian (Eames in lit.}. Although this is
probably correct, it is impossible to be certain on the present evidence that this
fauna is not Upper Oligocene in age. As mentioned above, it is often assumed that
Spiroclypeus does not occur in the Oligocene of the Mediterranean region, but proof
is lacking (see Adams 1967).
10. The Miocene orbitoidal limestones of Christmas Island
Jones & Chapman (1900) were the first to describe the foraminifera from these lime-
stones. Their material has been re-examined and additional thin sections prepared
from some of the original rock samples. Ludbrook (1965) published further valuable
information on the faunas and her material has also been examined. Additional
collections were made recently by Mr. J. Barrie (Bureau of Mineral Resources,
Canberra) and these are now being studied in conjunction with Dr. D. J. Belford.
Ludbrook (1965) dated the uppermost part of the limestone as Tf on the occurrence
in one sample (P33) of Flosculinella bontangensis , a species generally thought — but
never actually proved — to be restricted to strata of Tf age. Upwards of 500 samples
have now been collected from the limestones of the island but only in one locality is
there any suggestion of an age younger than Te. In this connection it is note-
worthy that ?33 also contains Borelis pygmaeus, a species characteristic of Tc-Te
and unknown from Tf. Ludbrook originally stated that Austrotrillina howchini
occurred in ?33 but this proved to be an error. All Ludbrooks' figured specimens of
A. howchini (op. cit., pi. 21, figs. 4-6) are good examples of A. striata.
11. Eocene limestones of New Caledonia
Through the courtesy of Professor M. F. Glaessner and Dr. J. Sigal, numerous thin
sections of Eocene limestones from New Caledonia in which Austrotrillina sp. nov.
was thought to occur (see Tissot & Noesmoen 1958), have been examined. These
organisms are now known to be different from Austrotrillina and are under investiga-
tion by Glaessner & Sigal.
III. SYSTEMATIC PALAEONTOLOGY
Family MILIOLID AE Ehrenberg 1839
Genus AUSTROTRILLINA Parr 1942
TYPE SPECIES Trillina howchini Schlumberger 1893.
(a) Shell structure
The shell wall is basically simple and may be regarded as consisting of three parts
(Text-fig. 3).
A REVISION OF A USTROTRILLIN A
81
i. A solid porcellaneous layer laid down over the outer surface of a previously
formed chamber. This was referred to as a " step " by Grimsdale (1952) who con-
sidered it to be of taxonomic importance. It is, in fact, inconstant in thickness,
FIG. 3. Wall structure of Austrotrillina (drawings all schematic). A. Generalized trans-
verse section through an adult chamber (a - alveolar layer; b - basal wall or " step ";
o — outer skin) B. " Striata " type wall with coarse alveoli, c. " Asmariensis " type wall
with fine, closely spaced alveoli. D & E. " Howchini " type wall with bifurcating alveoli.
E is more advanced than D. F. Wall of A. striata seen from inside the chamber. It is
clear that the spacing of the alveoli will vary according to the plane of section : a - a',
closely spaced; b - b', widely spaced. Non-oriented random sections can therefore
be misleading. The thickness of the outer skin is greatly exaggerated in these drawings.
both within a species and amongst the specimens from a single assemblage, and is of
no taxonomic value.
2. A curved outer wall consisting of two parts:
(a) a relatively thick, inner alveolar layer ;
(b) a very thin, non-alveolate, outer skin which is punctate externally.
The outer " skin " being very delicate is lost in most individuals. It can be de-
tected only rarely in specimens seen in thin sections of limestone, and then merely
as a dark line.
82 A REVISION OF AUSTROTRILLIN A
Alveoli may be fine as in A . asmariensis or coarse as in A . striata. The apparent
diameter of the alveoli varies according to the plane of section. This can be verified
by examining the inner surface of the wall (Text-fig. 3F; PI. 4, fig. 12).
In most specimens of A. striata and A. asmariensis, and in all the known specimens
of A. paucialveolata , the alveoli are simple tubes. The extent to which they are
present throughout the test seems to be a specific character.
In A . howchini the wall structure is more complex in that the alveoli bifurcate and
trifurcate towards their outer ends, i.e. towards the exterior of the shell (Text-fig.
3D, E), thus producing a pattern of long and short "septa" when seen in cross
section. In primitive forms, bifurcation begins at the chamber angles where the
wall is thickest, but in the most highly evolved forms the entire wall is involved.
EMENDED DIAGNOSIS. Test free, calcareous, porcellaneous; external wall con-
sisting of a thick alveolar inner part (except for that portion in contact with a
previous chamber) and a thin, finely pitted outer skin: chambers one half coil in
length: early chambers — in microspheric generation at least — added in quinquelo-
culine fashion, later chambers usually arranged in triloculine manner so that only
three are visible externally. Aperture probably pseudocribrate.
REMARKS. The alveolar wall and mode of growth are diagnostic for the genus.
The wall may be alveolate back to the second chamber, or the alveoli may be con-
fined to the last few chambers. Previous authors have regarded the triloculine
arrangement of the chambers as a constant and diagnostic feature, but this is not the
case. It is not unusual to find specimens with four chambers visible externally.
It should be noted that the figures given in the Treatise on Invertebrate Paleontology
(€474, figs 7, 8), although stated to be of the type species, are actually of A. striata
Todd & Post.
Todd & Post (1954) described the aperture of A. striata as cribrate, while Carter
(1964) stated that A. howchini has a pseudocribrate aperture. The present material
does not permit any comment on apertural characters.
The extremely thin outer skin is preserved only under very favourable circum-
stances.
(b) Description of species
Austrotrillina asmariensis sp. nov.
PI. I, figS. I-I2.
?I92O Trillina howchini Schlumberger ; Silvestri: 77, pi. 4, figs 9, 10.
?IQ29 Trillina howchini Schlumberger; Silvestri: 27, pi. 3, fig. 10.
1937 Trillina howchini Schlumberger; Silvestri: 81 (pars), pi. 6, fig. 3, ? pi. 5, fig. 3 only.
1947 Trillina howchini Schlumberger; Bursch: 12, pi. i, figs i, 2, pi. 3, fig. 14. Not text-fig. 3.
1956 Austrotrillina howchini (Schlumberger); van Bellen, pi. i, figs C, D.
?i957 Austrotrillina howchini (Schlumberger); Hanzawa: 38 (pars), pi. 22, figs 12, 13. Not
pi. 34, figs i, 2.
?I957 A ustrotrilli na howchini (Schlumberger); Cole: 329, pi. 101, figs 4-6.
1958 Austrotrillina howchini (Schlumberger); Smout & Eames: 208.
?i962 Austrotrillina howchini (Schlumberger); Dizer, pi. 3, fig. 7.
A REVISION OF AU STROTRILLIN A 83
TYPE LOCALITY: Kuh e Pataq (46° oo E. 34° 25' N.) N.W. Luristan, Iran.
TYPE LEVEL: Oligocene (almost certainly M. Oligocene, but above the last num-
mulites in the section). Sample JTP4Q43.
DIAGNOSIS: An Austrotrittina with a simple alveolar wall. Alveoli numerous,
normally ranging in diameter from 10 to 20 /.i.
HOLOTYPE. P47578.
A FORM
DESCRIPTION. Test comprising a globular or subglobular proloculus 0-07-0-25
mm. in internal diameter, followed by nine to fifteen chambers arranged as for the
genus. The chamber walls are rounded, and are alveolate except where in contact
with a previous chamber. The alveoli are numerous and simple. The walls of the
later chambers are usually 50-80^ in thickness but occasionally reach no/*.
All chambers after the second have alveolate walls. The nature of the aperture is
unknown.
Dimensions of the holotype
Length : unknown
Diameter : i-io x 1-78 mm.
Proloculus diameter: 0-2 x 0-18 mm.
Most specimens are relatively short (about i mm., few exceed 1-5 mm. in length),
and are between 0-5 and i-o mm. in diameter. Very compressed specimens, and
rare individuals in which the last chamber has been added at 180° to the penultimate
chamber, may be wider than this.
Variation. The shape of the test is not constant. Chambers margins are usually
bluntly rounded; many specimens are rather flattened or triangular in cross section.
Proloculus diameter is very variable, specimens from the Middle Oligocene some-
times having proloculi with a larger internal diameter than that of any other species.
B FORM
This differs from the A form in having more chambers (12-17 or more), a much
smaller proloculus, of which no measurements have been obtained, and a thicker
wall in the later chambers. The largest specimen so far seen is 2-3 mm. in diameter.
The last-formed chambers are more triangular in cross section than are those of the
A forms. The wall attains a maximum thickness of about 0-15 mm.
VARIATION: Two specimens show a tendency for the alveoli to bifurcate in the
last two chambers.
ASSOCIATED FAUNA: i. Type level: Peneroplis evolutus, P. thomasi, Praer-
hapydionina delicata.
2. Lower levels (according to Dr. T. D. Adams): Archaias asmaricus, Borelis,
Eulepidina, Nummulites fichteli, Meandropsina anahensis. The occurrence of
A. asmaricus and M. anahensis so low in the Tertiary requires verification.
84 A REVISION OF AUSTROTRILLIN A
REMARKS: This species has frequently been confused with A. howchini in the
past, and many records of the latter from the Middle and Far East really refer to
A. asmariensis.
The earliest definite occurrence of the species is in the Asmari Formation at Kuh e
Pataq where it occurs in beds which, on the available evidence (see p. 76), can be
assigned tentatively to the Lower Oligocene. It occurs commonly in the Middle
Oligocene of the same section and in the Shurau Formation of Iraq, which is also
M. Oligocene; good specimens have been found in two museum samples from
surface exposures in Iran, in each case in association with Nummulites fichteli,
an indication that these rocks cannot be younger than Middle Oligocene and could
be Lower Oligocene in age. Neither sample contained Lepidocyclina.
In the Shurau Formation A. asmariensis is often associated with A. paucial-
veolata. It occurs abundantly in the Bajawan Formation of Iraq and in derived
pebbles in the lower part of the Lower Fars conglomerate: it is common in the
middle part of the Asmari limestone.
Silvestri's records from Somalia (1937), said to be from the Oligocene or Miocene
are, in part at least, from the Oligocene. Of his illustrated specimens, pi. 5, fig. 2,
is a largely recrystallized form which might fairly be assigned to A . paucialveolata ;
pi. 5, fig. 3 is not very clear, but pi. 6, fig. 3 is almost certainly A. asmariensis.
In no case were these specimens associated with an age-diagnostic fauna, nor were
they from successions the ages of which could be determined with certainty.
Records of A. howchini (Silvestri 1920, 1929) from the island of Paxos and from
Otranto, Apulia, southern Italy, probably refer to this species, although the figures
are not really good enough for this to be certain.
Dizer (1962) has recorded A. howchini, from beds of supposed Burdigalian age in
various parts of N.W. Turkey. Unfortunately, her best illustration is almost in-
determinable as details of the wall structure cannot be seen. However, the shape of
the chambers strongly suggests that the specimen is A. asmariensis. Dizer's other
illustration (pi. i, fig. 16) is unrecognizable owing to poor preservation.
Specimens indistinguishable from A. asmariensis are frequently met with in
random sections of limestones from the Indo-Pacific where they occur at about the
same levels as A . striata. They apparently occur in all the known Te limestones of
Sarawak and have been seen in the Te limestones along the Kinabatangan River in
Sabah and in Te limestones from Saipan (see p. 93). They occur in the Melinau
limestone and were referred to the A. striata / 'howchini group by the author (1965).
A. asmariensis differs from typical specimens of A. paucialveolata and A. striata
in having an inner wall that is clearly alveolar back to the third chamber in the
A form. It differs from A . striata in having more numerous and much smaller al-
veoli. It differs from A. howchini in having simple (i.e. non-bifurcating) alveoli, a
thinner wall and a more open chamber lumen in the adult stage (see Table i).
GEOGRAPHICAL DISTRIBUTION: Middle East, East Africa, south-east Asia, Pacific
Islands.
STRATIGRAPHICAL RANGE:? Lower or Middle Oligocene to Lower Miocene in the
Tethyan region: Te in the Indo-Pacific region.
A REVISION OF AUSTROTRILLIN A 85
Note: Although typical specimens of A. asmariensis and A. striata (cf. PL i,
figs 4, 7, n, and PI. 4, figs n, 4, 13) look very different, the geographical and strati-
graphical distributions of the two are such that it is difficult to avoid the conclusion
that we are really dealing with one species and that the differences between them are
not of fundamental importance. Nevertheless, pending the discovery of matrix-
free specimens of A. asmariensis and a concomitantly more detailed description, it is
advisable to regard it as a distinct species.
Austrotrillina brunni Marie
PI. 6, figs 6, 8
1955 Austrotrillina brunni Marie: 203, pi. 19, figs 4-8.
REMARKS. The only record of this species is from a limestone a few metres thick
within " une immense succession greseuse " to the north-west of the village of
Pentafolon in north-west Greece. The limestone was dated as Upper Oligocene or
basal Aquitanian on the occurrence of Miogypsinoides complanatus (Schlumberger) .
The only other foraminifera listed from it are Lepidocydina (Nephrolepidina) sp.,
which occurs in abundance, and Rotalia sp.
It has not been possible to examine the thin sections in which this species was
found, but Dr. P. Marie has kindly made available the original photographs on which
the figures on pi. 19 of his paper were based. The reproduction of these photo-
graphs in Marie's paper is, unfortunately, not good enough for the internal structure
to be clearly discerned. However, the photographs show that the structure of the
wall is, in some specimens at least, fairly advanced in type, i.e. the alveoli bifurcate
towards their outer ends. On the other hand, in other specimens there is no sign of
bifurcation, and these resemble the A. striata I asmariensis group. In all specimens
the chambers are rounded in cross section and in this respect are unlike the Australian
representatives of A. howchini. They resemble forms found in Upper Te in the
Indo-Pacific region, i.e. they are intermediate between the A. striata /asmariensis
group and the true A . howchini.
On the present evidence it is impossible to assign an accurate age to the Pentafolon
limestone. The wall structure of the Austrotrillina specimens suggests that the rock
is late Aquitanian in age. The presence of M. complanatus is not a sufficient indica-
tion of age since it ranges from the Oligocene into the early Miocene. Its upper limit
does not appear to have been established satisfactorily. Eames (in lit.) has in-
dicated that M. complanatus is common in late Aquitanian beds in the Middle East ;
Renz (1936) recorded it from Italy with Miogypsina irregularis (Michelotti) (= M.
globulina (Michelotti)) a species usually considered to be " Burdigalian " in age, and
Gordon (1961) has reported it from " above the Orbulina surface ", i.e. from " Burdi-
galian " or younger rocks, in Puerto Rico. A further examination of the limestone is
necessary to establish whether or not it contains foraminifera that would substantiate
an Aquitanian age.
Marie believed that the rounded nature of the chambers and, therefore, of the test,
was sufficient to distinguish this species from A . howchini. The present author does
86 A REVISION OF AUSTROTRILLINA
not share this view. While the youngest Australian representatives of A . howchini
have triangular chambers, many advanced Tf forms from New Guinea, East Africa
and India have rounded chambers. Marie also laid emphasis on the quinqueloculine
arrangement of the chambers in A . brunni. They are, however, more triloculine than
quinqueloculine and are similar to those of A . striata, a species which often shows four
chambers externally (see PL 4, fig. 9).
It is thought that the name A . brunni should be retained until such time as oriented
sections made from additional material can be compared with sections of other species
of the genus.
Austrotrillina howchini (Schlumberger)
PI. 2, figs 1-7; PI. 6, figs 1-5, 7
1893 Trillina howchini Schlumberger; 119, text-fig, i, pi. 3, fig. 6.
1908 Trillina howchini Schlumberger; Chapman: 753, pi. 39, figs 7-9.
1913 Trillina howchini Schlumberger; Chapman: 169, pi. 16, fig. 4.
1927 Trillina howchini Schlumberger; Davies: 10, pi. 2, figs 10, n.
?i927 Trillina howchini Schlumberger; van der Vlerk & Umbgrove: 13, text-fig. 2.
1936 Trillina howchini Schlumberger ; Renz: 32, pi. 15, figs 4, 5.
1936 Trillina howchini Schlumberger; Crespin: 6, pi. i, figs i, 2.
1941 Trillina howchini Schlumberger; Rao: 7, pi. 2, fig. 7.
1942 Austrotrillina howchini (Schlumberger); Parr: 361-2, figs 1-3.
1954 Austrotrillina howchini (Schlumberger); Crespin: 40, pi. 7, fig. 14.
1955 Austrotrillina howchini (Schlumberger); Crespin: 60-1, pi. 9, fig. 4.
?i957 Austrotrillina howchini (Schlumberger); Hanzawa: 38 (pars), pi. 34, figs, i, 2. Not
pi. 22, figS 12, 13.
1962 Austrotrillina howchini (Schlumberger); Eames et al., pi. 6, figs B, E.
1964 Austrotrillina howchini (Schlumberger); Carter: 62, pi. i, figs 12-17.
DIAGNOSIS. An Austrotrillina with a smooth, finely pitted test; wall thick, with
closely spaced alveoli which bifurcate — sometimes more than once — towards their
inner ends to form secondary and tertiary alveoli.
A FORM
DESCRIPTION. Test comprising a subglobular proloculus (0-07-0-15 mm. in
diameter) followed by a tube-like second chamber ; subsequent chambers arranged in
a triloculine manner so that not more than three are visible externally. The shell
normally consists of from ten to twelve chambers (proloculus excluded). The
non-alveolar outer skin is very thin (5-10 //) and is covered with fine, shallow pits.
The inner layer is thick, alveolate, the alveoli bifurcating as they approach the outer
skin so that primary, secondary and tertiary alveoli appear. The dividing walls
between the secondary and tertiary alveoli are always much shorter than the
primary dividing walls and thus appear as short " septa " in transverse sections.
The alveoli make a sharp turn as they reach the outer skin and end blindly (PI. 2,
fig. 6). Transverse sections cut through the upturned ends of the alveoli produce
the impression of vertical canals (PI. 2, fig. 3). The alveolar layer is always thickest
at the chamber angles ; it often occludes much of the chamber lumen. The aperture
is pseudocribrate according to Carter (1964).
A REVISION OF AUSTROTRILLINA 87
B FORM
Only one specimen available.
Similar to the A form but with a much smaller proloculus. Test composed of at
least sixteen chambers.
MEASUREMENTS : length : not recorded, but not noticeably greater than that of
the A form
diameter: 2-14 X 1-35 mm.
wall thickness : 0-17-0-35 mm.
VARIATION: In most specimens, especially those from Australia, the chambers
are triangular in shape rather than rounded.
REMARKS. Schlumberger described the A form of this species from Muddy Creek,
Hamilton, Victoria, southern Australia, and the B form from the Philippines. How-
ever, in the absence of an adequate figure and description of the latter form there is no
certainty that he was describing the same species. Carter (personal communication)
has recently confirmed that it is impossible to tell either the exact locality or the
horizon from which Schlumberger 's Australian specimens came. The only beds in
Victoria from which matrix-free specimens can now be obtained are poorly exposed at
Gippsland.
Most of the specimens described here come from the Pata limestone, penetrated in
a boring at the Chowilla Dam Site, River Murray, South Australia. Ludbrook
(1961; 1963) assigned this limestone to the uppermost Burdigalian on the ground
that it contained A. howchini together with Orbulina universa. It is thus approx-
imately that same age as the Trealla limestone in West Australia. Ludbrook (1963)
also notes that A. howchini occurs with Flosculinella bontangensis (Rutten) and
Marginopora vertebralis Blainville (the former is a typical Lower Tf or " Burdigalian "
species) in the Nullarbor limestone of the Eucla Basin, South Australia.
A . howchini has been recorded fairly frequently from the Miocene of Australia and
is known from the Cape Peninsula in the west (Crespin 1955) to Victoria in the south.
It occurs in beds of Lower Tf age in the Tulki and Trealla limestones of west
Australia. In the Trealla limestone it is associated with Orbulina universa as well as
with numerous other Tf marker fossils. In Victoria (Carter 1964) it appears two
zones below Orbulina universa and 0. suturalis and gives its name to a zone.
Most records of A. howchini from outside Australia are, unfortunately, incorrect.
The only occurrences known to the writer that can be properly substantiated are as
follows.
1. Lower Miocene limestones of the Malabar coast. Cochin, Travancore, India.
In these limestones A. howchini occurs together with Taberina malabarica. These
beds were said by Carter (1853) to be Pliocene in age, but the foraminifera prove
otherwise. Carter did not mention A. howchini, but it is a common species in his
samples (see pi. 6, figs 2, 4, 5). It also occurs in Miocene conglomerates in the
Tapti area, western India (Rao 1941).
2. In the Lower Miocene limestones of Ceylon, A. howchini occurs with Taberina
malabarica. Wayland & Davies (1923) also reported Flosculinella and Spiroclypeus
from these limestones. The latter genus was stated to be represented by two speci-
GEOL. 1 6, 2 8
88 A REVISION OF AUSTROTRILLINA
mens. It does not occur in any of the three slides deposited in the British Museum
(Natural History), neither has it been found in additional samples recently examined.
Its occurrence in this limestone is therefore open to doubt. The specimens referred
by Davies to Flosculinella are very poorly preserved and may or may not belong to
this genus. The evolutionary stage reached by the wall structure of the Austro-
trillina specimens from these samples allows the rock to be dated as Lower Tf or
" Burdigalian ". Flosculinella commonly occurs in strata of this age whereas
Spiroclypeus does not.
3. Lower Miocene limestones of East Africa: A. howchini occurs with T. mala-
barica, Miogypsina thecidaeformis and Miogypsinoides dehaarti in the Lower Chake
beds of Pemba Island, and with T. malabarica in beds of a similar age in the Hadu-
Fundi Isi area of Kenya. Following the recent discovery of Flosculinella bontan-
gensis in the Chake Chake beds (Eames et al. 1962) these can be regarded as Lower Tf
in age. F. bontangensis alone, cannot as yet be considered as diagnostic of Tf, but in
the light of the evidence presented in this paper its occurrence with A. howchini s. s.
does constitute a satisfactory indication of age.
4. The Melinau limestone, Sarawak: In the uppermost part of this limestone
(Upper Te) specimens transitional from A. asmariensis to A. howchini occur (PL 5,
figs I, 4). Planktonic foraminifera, including Praeorbulina cf. glomerosa (Blow),
occurring in samples collected in 1966 from the highest beds in the Terikan River,
indicate that the top of the limestone is in Zone N8 of Banner & Blow (1965) and not
in the C. dissimilis Zone as previously suggested (Adams 1965). Primitive repres-
entatives of A. howchini have also been seen in bore-hole material from the Suai
Baram area, Sarawak.
5. Saipan: A problem arises in connection with the fauna of the Tagpochau
limestone. Cole (1957) regarded this limestone as Te in age while Hanzawa (1957)
thought that at least part of it was Tf. Hanzawa (1957, table 2, sample g; table 4,
sample 3) reported Spiroclypeus tidoenganensis and Orbulina universa as occurring
together in samples from Saipan and Tinian. However, an examination of the very
numerous Miocene samples from Saipan deposited in the U.S. National Museum
has failed to reveal Orbulina in association with Spiroclypeus. Reasonable doubt
therefore exists about the accuracy of some of Hanzawa's determinations of one or
other of these genera. Both A . striata and A . howchini occur on Saipan. The former
species is the more common, the latter occurring only in a small number of samples
(e.g. 6413).
Although the common species in Saipan is A . striata, specimens indistinguishable
from A. asmariensis are sometimes seen in random thin sections. This is also true
of the Bornean limestones. Whether this means that A. asmariensis and A. striata
are really synonymous, or that the range of variation of some characters overlaps is
not clear. However, when total assemblages are considered there is no difficulty in
deciding which species is present.
6. Pacific Isles: Todd & Low (1960) stated that A. howchini occurred in the
upper part (iioo-mo ft.) of Eniwetok drill hole E-i and from 560-570 ft. in F-i.
A REVISION OF AUSTROTRILLINA 89
These authors kindly allowed the writer to examine and section the specimens on
which their identification was based. This study showed that the two lowest speci-
mens should have been referred to A. striata and the highest to " miliolid gen. et
sp. indet." Similarly, the specimens described as A. howchini by Todd & Post
(1954) from Bikini are also incorrectly identified. It should be said that these
identifications were based on the external appearance of the tests, all of which were
decorticated. We now know that external appearances can be misleading, but this
was not known when the Bikini and Eniwetok bores were first examined. It can
therefore be stated that no specimens of A. howchini are known from the Pacific
Isles east of Saipan although it is probably only a matter of time before they are
discovered.
Most records of A . howchini from the Far East are impossible to verify as they are
unaccompanied by figures. However, it is probable that all records of A. howchini
from beds of Tf age can be accepted as correct, except where the dating depends on
the presence of Austrotrillina, This is certainly true of New Guinea where excellent
examples of A. howchini occur in Tf limestones. Records from beds of Upper Te
age cannot be accepted at their face value unless accompanied by figures : records
from beds of Td and Lower Te age are almost certainly incorrect, and in all pro-
bability refer either to A. asmariensis or to A. striata.
7. Europe and the Middle East: The only definite record of A. howchini from
Europe appears to be that of Renz (1936) who reported it from the Burdigalian
of the central Apennines. His specimens have been examined. Austrotrillina
brunni, from the Lower Miocene of Greece is not, of course, far removed from A.
howchini and is very probably a transition form from A. striata (see below). The
specimens illustrated by Silvestri (1920, 1929) seem to have a simpler wall structure
than A. howchini s. s. Hottinger's record (1963) of this species from the Oligo-
cene of Spain is really of A. paucialveolata.
Dizer's record (1962) of A . howchini from the Miocene of the Sivas Basin, Turkey,
is almost certainty incorrect as was indicated earlier (p. 84).
Stefanini's record (1921 : 124) of A. howchini from the Oligocene of Cyrenaica is
unacceptable as his figured specimen is not even recognizable as Austrotrillina.
The writer has, however, seen specimens of the A. striataj asmariensis type from early
Miocene deposits of Libya.
GEOGRAPHICAL DISTRIBUTION : Known from Europe, East Africa, India, Indonesia,
New Guinea, Saipan and Australia.
STRATIGRAPHICAL DISTRIBUTION: Mainly Lower Tf (= " Burdigalian " of
Europe). Transitional forms from A. striata and A. asmariensis occur in Upper
Te beds of south-east Asia and Saipan.
Austrotrillina paucialveolata Grimsdale
PI. 3, figs 1-6
?i937 Trillina howchini Schlumberger ; Silvestri (pars) : 81, pi. 5, fig. 2.
1952 Austrotrillina paucialveolata Grimsdale: 229, pi. 20, figs. 7-10.
1956 A ustrotrillina paucialveolata Grimsdale; van Bellen, pi. 3, fig. A, pi. 6, fig. B.
GEOL. 1 6, 2 8§
90 A REVISION OF AUSTROTRILLIN A
?i962 Austrotrillina paucialveolata Grimsdale; Dizer: 43-4, pi. 2, figs i, 2.
1963 Austrotrillina howchini (Schlumberger) ; Hottinger: 964, pi. i, figs i, 2.
EMENDED DIAGNOSIS. An Austrotrillina with simple alveoli restricted to the
last few chambers.
A FORM
DESCRIPTION. Test comprising a proloculus, a tube-like second chamber and up
to fourteen further chambers arranged roughly in a triloculine fashion. The alveoli
are simple and appear to be confined to the last four to six chambers. The diameter
of the proloculus ranges from 0-08 to 0-13 mm. in the few specimens measured.
The nature of the aperture and the surface appearance of the test are unknown.
B FORM
Only a few off-centre sections available. Larger than the A form, and pre-
sumably with more chambers. Maximum number of chambers observed is thirteen.
Wall up to 0-15 mm. thick. Maximum observed diameter 2-15 mm.
REMARKS. The original description of this species is extremely short and has not
previously been emended. Grimsdale only stated that the alveoli were coarser than
in A. howchini. However, the specimens he had in mind when making this com-
parison were not A. howchini s. s. but A. asmariensis sp. nov. as is shown below.
After examining Grimsdale's syntypes, specimens from the Iraq Petroleum Com-
pany's collections in London, and large numbers of thin sections from the Asmari
limestone in the Gach Saran oilfield (Gach Saran wells 6 and n) and from Kuh e Pataq
and Kuh e Kalagh, the following conclusions have been reached:
1. All the specimens of A. paucialveolata so far described from the type area are
poorly preserved, and the apparent coarseness and irregularity of the alveoli is due
in all cases to poor preservation caused by recrystallization of the limestone and of
the shell walls.
2. Grimsdale's specimens included both A and B forms although he appears to
have been unaware of this. The two largest figured syntypes were probably both
B forms.
3. The " step " described by Grimsdale is a thickening of the basal wall. It
is not a constant character but varies in development amongst specimens from the
same population. It is very prominent in some individuals of A. striata (PL 4,
fig. 13) and A. howchini (PL 2, fig. 3), and occurs to some extent in all representatives
of the genus.
4. A . paucialveolata occurs with A . asmariensis (= A. howchini sensu Grimsdale
and van Bellen) in the Lower Asmari limestone.
5. The only diagnostic features of this species seem to be the restriction of the
alveoli to the last few chambers, coupled with the fact that the walls of the early
chambers appear to be thick. These features could, however, be recrystallization
effects.
A REVISION OF AUSTROTRILLIN A 91
6. There is no evidence as yet that A . paucialveolata occurs at stratigraphically
lower levels than A. asmariensis. However, since it has not so far been reported
above the Middle Oligocene it is worth regarding as separate from A. asmariensis
for the present.
If future work on isolated, matrix-free specimens shows conclusively that A.
paucialveolata and A . asmariensis are synonymous, then the former name will have
priority regardless of the fact that it will be inappropriate descriptively.
Grimsdale (1952) described this species from the Miliola limestone of the Kirkuk
oilfield, Iraq, stating in his plate explanation that the syntypes came from Kirkuk
Well no. 14. No depth or horizon was given. The age was stated to be Oligocene,
but from the information given in his text (p. 224) it is impossible to deduce whether
it is Lower, Middle or Upper Oligocene. Although not specifically stated, the im-
plication is that the Miliola limestone is younger than Lower Oligocene since it
rests on beds of undoubted Lower Oligocene age.
Van Bellen (1956) described Kirkuk Well 14 in detail, and figured additional
specimens of A. paucialveolata. Examination of van Bellen's plate revealed that
among the ten specimens figured were the three original syntypes of Grimsdale.
Van Bellen was apparently unaware of this as he made no mention of it in the text.
This refiguring is extremely fortunate since it fixes the exact horizon of the types as
34 feet below the Lower Fars Conglomerate, i.e. in the Shurau Formation. This
Formation in Kirkuk Well 14 is only thin, 30 ft. at most, whereas in the type section
(Well Kiog) it is 60 ft. thick. From van Bellen's paper it seems probable that the
Shurau Formation is of late Lower Oligocene age, since it conformably overlies the
Sheikh Alas Formation of undoubted Lower Oligocene age (contains Nummulites
fichteli without Eulepidina] and is itself disconformably overlain by the Baba
Formation — presumably Middle Oligocene in age since it contains both N. fichteli
and Lepidocyclina spp.
Silvestri's (1937) record of this species was discussed by Grimsdale (1952) and
nothing further can be added here. The only other record from the Middle East
seems to be that of Dizer (1962). Her figures are obviously of poorly-preserved
specimens and she gives no description.
It is significant that the material described by Grimsdale and van Bellen came from
the same well, and it is even more significant that van Bellen recorded A. howchini
(really A. asmariensis sp. nov. or A. striata) from the same level in this well. In
correspondence, Dr van Bellen has confirmed that A . paucialveolata and the species
he called A . howchini are known in association in at least two other wells.
The only reliable record of A . paucialveolata from outside the Middle East is that
of Hottinger (1963) who recorded it as A. howchini from the Oligocene of Spain.
Hottinger's specimens have been examined and two of them are figured here (PI. 3,
figs 5, 6).
GEOGRAPHICAL DISTRIBUTION: Iraq, Iran, Spain, Turkey.
STRATIGRAPHICAL RANGE : Only known with certainty from the highest part of the
? Lower Oligocene or from the Middle Oligocene of the Middle East, and from the
Oligocene (? Middle Oligocene) of Spain.
92 A REVISION OF AUSTROTRILLINA
Austrotrillina striata Todd & Post
PL 4, figs 1-13 i PI- 6, fig. 9
1954 Austrotrillina striata Todd & Post: 555, pi. 198, fig. 9.
1954 Austrotrillina howchini (Schlumberger) ; Cole: 573, pi. 210, figs. 6-9.
1960 Austrotrillina striata Todd & Post; Todd & Low: 825, pi. 261, fig. 22.
1965 Austrotrillina howchini (Schlumberger); Ludbrook: 292, pi. 21, figs. 4-6.
DIAGNOSIS: A species of Austrotrillina distinguished by its simple, coarse alveoli
and finely striate surface.
A FORM
DESCRIPTION: Test comprising a spherical proloculus (0-05-0-13 mm. in diameter)
followed by up to sixteen chambers arranged in a quinqueloculine fashion. The
inner layer of the wall is thick and does not become markedly alveolate until the
fifth or sixth chamber. The alveoli are mainly simple and are coarse. Their
apparent width, seen in thin section, depends on the plane through which the wall
is cut (see Text-fig. 3 F, pi. 4, fig. 12). The lumen of the chambers remains open
throughout the adult stage. The outer, non-alveolate, skin is very thin (10-15 /*).
finely pitted, and ornamented by fine striae which tend to become coarser on the
apices of the external margins. Wall thickness ranges from 0-06-0-11 mm. (usually
0-06-0-08 mm.). The chambers are rounded in transverse section. Many topotype
specimens are only weakly striate, a few are possibly non-striate. Aperture cribrate
according to Todd & Post (1954).
B FORM
PI. 5, fig. 9, (not from type area).
DIAMETER: 1-28 x 0-78 mm.
WALL THICKNESS: 0-08-0-18 mm.
PROLOCULUS DIAMETER: 0-025 mm- Nineteen chambers visible.
REMARKS: The original figures of this species are somewhat misleading in that
they show only a few relatively coarse striae in the centre of the test. Inspection
of numerous topotypes has shown that in typical specimens the whole wall is very
finely striate (PI. 4, fig. 9). This species was originally said to differ from A . howchini
in its striated surface, much coarser textured alveoli, and in being less distinctly
triangular in transverse section. No thin section showing the wall structure was
figured. Cole (1954), in a companion publication in the same volume, figured thin
sections of a form he called A . howchini from the same levels in the Bikini drill hole as
the types of A. striata. These specimens have been examined and there is no doubt
that most of them are examples of A. striata.
As mentioned earlier, Cole's figures were, unfortunately, reproduced in good faith
by Loeblich & Tappan as A. howchini. It should be noted that the surface striae
do not show up in thin sections. The alveoli in Cole's specimens are very like those
seen in some individuals of A. asmariensis. In a few specimens there is a tendency
A REVISION OF AUSTROTRILLIN A 93
for the alveoli to bifurcate (PL 3, fig. 9), but this is not pronounced or common.
Such individuals are intermediate between A . striata and A . howchini.
GEOGRAPHICAL DISTRIBUTION: The Pacific Isles, Indonesia, Christmas Island,
i.e. Indo-Pacific. Perhaps also the Tethyan region. Specimens seen by the writer
from the Lower Coralline limestone of Malta (PI. 3 fig. 7) are best referred to as
A . cf . striata for the time being.
STRATIGRAPHICAL RANGE: Uppermost Td and throughout Te in the Indo-
Pacific. Uncertain in the Tethyan region, but probably Upper Oligocene and
lowermost Miocene (Aquitanian) .
Limestones of Upper Te age in Borneo, Saipan and Christmas Island all contain
Austrotrillina specimens that are morphologically intermediate between A. striata
and A . howchini. True specimens of A . striata always occur in the same populations.
There can be no doubt that A . howchini evolved from A . striata in Upper Te times.
(c) Outstanding problems
1. Detailed descriptions of A. asmariensis, A. paucialveolata and A. brunni
based on matrix-free specimens are necessary. Until these become available it will
be impossible to decide the exact relationships of these species to each other and to
A. striata.
2. More precise information is needed on the ranges of all the species. In parti-
cular, it would be interesting to know whether or not A. asmariensis and A.
paucialveolata occur in undoubted Lower Oligocene beds outside the Middle East.
IV. CONCLUSIONS
On present evidence it is possible to recognize five species of Austrotrillina in
rocks of ? Lower or Middle Oligocene to Lower Miocene age. The type species,
A. howchini, has a more complex wall structure than the others and represents the
end point in the evolution of the genus. Two species, A. brunni and A. paucial-
veolata, are poorly known and of uncertain stratigraphical value. The others are
extremely useful for correlation.
The most important characters for species differentiation are (a) the structure of
the inner wall and (b) the type of surface ornament. In all other respects the tests
are remarkably similar, a fact that may be taken to indicate a monophyletic origin
for the genus. There seem to be no significant differences in the size of test, dia-
meter of the proloculus or number or arrangement of chambers between the species.
The distinguishing characters for the various species are set out in Table i.
The identification of species of Austrotrillina is a relatively simple matter provided
that preservation is reasonably good and that oriented sections, or a sufficient
number of random sections, are available. It is, however, dangerous to try to
distinguish between A. asmariensis, A. paucialveolata and A. striata on badly pre-
served material or on rare random sections in limestones. Members of the Miliolidae
are amongst the first foraminifera to be affected by recrystallization, and Austro-
trillina, because of its alveolar wall, is particularly prone to partial destruction.
94
A REVISION OF AUSTROTRILLINA
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A REVISION OF AUSTROTRILLINA 95
Austrotrillina appeared in the Oligocene of the Middle East, its first recorded
occurrence being with Nummulites fichteli. The earliest known forms can be
assigned to A. asmariensis. In the Shurau Formation of Iraq, A. asmariensis occurs
alongside A. paucialveolata. The latter species does not appear to have achieved a
wide geographical or stratigraphical distribution; it is based on recrystallized or
otherwise badly preserved specimens and may eventually prove to be synonymous
with A. asmariensis or A. striata.
A. asmariensis persisted virtually unchanged from the Middle Oligocene into the
Lower Miocene (Aquitanian) . In the Indo-Pacific, A. striata appeared in late Td
times and persisted through Te. It is possible that these are two forms of the same
species.
Present evidence indicates that the transition from A. striata to A. howchini
began in Upper Te times in the Indo-Pacific and that this process was complete by
Tf times. In Lower Tf times (" Burdigalian " in the Tethyan region) all known
representatives of the genus were of the advanced A. howchini type. This last
species was widely distributed, ranging from the western Tethys to Australia.
The writer believes that all the species of Austrotrillina belong to a single lineage
and that, in a sense, they all belong to one species. The evolutionary changes shown
by the test will allow us to delimit a number of " species " which are of value strati-
graphically. These specific names should be maintained for as long as they can be
shown to be of stratigraphical value.
V. REFERENCES
ADAMS, C. G. 1965. The Foraminifera and stratigraphy of the Melinau limestone, Sarawak
and its importance in Tertiary correlation. Q. Jl. geol. Soc., London, 121 : 283-338, pis. 21-
3°-
— 1967. Tertiary foraminifera in the Tethyan, American and Indo-Pacific Provinces. Pp.
195-217. In: Aspects of Tethyan Biogeography , Eds. C. G. Adams & D. V. Ager, Systematics
Association Publication No. 7, London. 336 pp.
BANNER, F. T. & BLOW, W. H. 1965. Progress in the planktonic foraminiferal biostrati-
graphy of the Neogene. Nature, London, 208: 1164-1166.
BELLEN, R. C. VAN 1956. The stratigraphy of the " Main Limestone " of the Kirkuk, Bai
Hassan and Qarah Chauq Dagh structures in north Iraq. /. Inst. Petrol., 42, no. 393:
233-263. 8 pis.
BURSCH, J. G. 1947. Mikropalaontologische Untersuchungen des Tertiars von Gross Kei
(Molukken). Schweiz palaeont. Abh., 65 : 1-69, pis. 1-5.
CARTER, A. N. 1964. Tertiary Foraminifera from Gippsland, Victoria, and their strati-
graphical significance. Mem. geol. Surv. Viet., 23 : 1-154, I7 P^s-
CARTER, H. J. 1853. Description of Orbitolites malabarica, illustrative of the spiral and not
concentric arrangement of chambers in d'Orbigny's Order Cyclostegues. Ann. Mag. nat.
Hist., London (2) 11 : 142-144, pi. nA.
CHAPMAN, F. 1908. On the Tertiary limestones and foraminiferal tuffs of Malekula, New
Hebrides. Proc. Linn. Soc. N.S.W., 32 : 745-760, pis. 37-41.
1913. Description of new and rare fossils obtained by deep boring in the Mallee. Part
i — Plantae; and Rhizopoda to Brachiopoda. Proc. R. Soc. Viet, (n.s.) 26 : 165-191, pis,
16-19.
96 A REVISION OF AUSTROTRILLINA
COLE, W. S. 1954. Larger foraminifera and smaller diagnostic foraminifera from Bikini drill
holes. Prof. Pap. U.S. geol. Surv., 260-0 : 569-608, pis. 204-222.
1957- Larger foraminifera of Saipan Island. Prof. Pap. U.S. geol. Surv., 280-1 : 321-
360, pis. 94-118.
1958. Larger foraminifera from Eniwetok Atoll drill holes. Prof. Pap. U.S. geol Surv.,
260-v: 743-784. Pls- 231-249.
CLOUD, P. E., SCHMIDT, R. G. & BURKE, H. W. 1956. Geology of Saipan, Mariana Islands.
Prof. Pap. U.S. geol. Surv., 280A : 1-126.
CRESPIN, I. 1936. The larger foraminifera of the Lower Miocene of Victoria. Palaeont. Bull.,
Canberra, 2 : 3-13, pis. 1,2.
1954- Stratigraphy and Micropalaeontology of the Marine Tertiary rocks between
Adelaide and Aldinga, South Australia. Bull. Bur. Miner. Resour. Geol. Geophys. Aust.,
Rep. No. 12 : 1-65, pis. 1-7.
- !955- The Cape Range structure Western Australia: pt. 2 Micropalaeontology. Bull.
Bur. Miner. Resour. Geol. Geophys. Aust., 21 : 49-82, pis. 7-10.
EAMES, F. E., BANNER, F. T., BLOW, W. H. & CLARK, W. J. 1962. Fundamentals of Mid-
Tertiary stratigraphical correlation. London (Cambridge University Press).
DAVIES, A. M. 1927. Lower Miocene Foraminifera from Pemba Island, pp. 7-12. In:
Stockley G. M. (see below). Report. Palaeont. Zanzibar Protectorate.
DIZER, A. 1962^. Les foraminiferes de 1'Eocene et 1'Oligocene de Denizli. Rev. Fac. Sci.
Univ. Istanbul (B) 27 : 39-47, pis. 1-7.
- 19626. Foraminifera of the Miocene of the Sivas Basin (Turkey). Rev. Fac. Sci. Univ.
Istanbul (B) 27 : 49-85, pis. 1-9.
GORDON, W. A. 1961. Foraminifera from the 4CPR oil test well near Arecibo, Puerto Rico.
Publ. Puerto Rico Mining Comm., 1961 : 25-40.
GRIMSDALE, T. F. 1952. Cretaceous and Tertiary foraminifera from the Middle East. Bull.
Br. Mus. nat. Hist. (Geol.) 1 : 221-248, pis. 20-25.
HANZAWA, S. 1957. Cenozoic foraminifera of Micronesia. Mem. geol. Soc. Am., 66 : 1-163,
pis. 1-38.
HOTTINGER, L. 1963. Cjuelques Foraminiferes porcelanes oligocenes dans la serie sddimentaire
prebetique de Moratalla (Espagne m6ridionale) . Eclog. geol. Helv., 56 : 963-972, pis. 1-5.
HOUSE, M. R., DUNHAM, K. C. & WIGGLESWORTH, J. C. 1961. Geology and structure of the
Maltese islands : 25-33. In: Bowd en- Jones, Dewdney & Fisher. Malta; Background for
Development, Newcastle.
JONES, T. R. & CHAPMAN, F. 1900. On the foraminifera of the orbitoidal limestones of
Christmas Island: 226-264, pis. 20, 21. In: Andrews, C. W. A monograph of Christmas
Island (Indian Ocean). Brit. Mus. (Nat. Hist.), London.
LOEBLICH, A. R. & TAPPAN, H. 1964. Sarcodina chiefly " Thecamoebians " and Foramini-
ferida. Treatise on Invertebrate Palaeontology, Pt.C, Protista 2. Geol. Soc. Amer. & Univ-
ersity of Kansas Press.
LUDBROOK, N. H. 1961. Stratigraphy of the Murray Basin in South Australia Bull. Geol.
Surv. S. Aust., 36 : 1-96.
— 1963. Correlation of the Tertiary rocks of South Australia. Trans. Roy. Soc. S. Aust.,
87 : 5-15-
— 1965. Tertiary fossils from Christmas Island (Indian Ocean) Jl. geol. Soc. Australia,
12 : 285-294, pis. 21, 22.
MARIE, P. 1955. Quelques formes nouvelles de Polypiers et de Foraminiferes de 1'Oligocene
et du Miocene du N.W. de la Grece. II Foraminiferes. Bull. Soc. geol. Fr. (6) 5 : 193-205,
pis. 18-20.
PARR, W. J. 1942. New genera of foraminifera from the Tertiary of Victoria. Min. geol. Jb.,
2 : 361-363.
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descriptions of foraminifera of the genus Pellatispira from the Upper Eocene of this region.
Half yearly Jl., Mysore University (n.s.B), 2 : 5-17, pis. i, 2.
A REVISION OF AUSTROTRILLIN A
97
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(Obere Kreide-Tertiar) im zentralen Appenin. Eclog. geol. Helv., 29 : 1-149, pis. 1-15.
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— 1929. Osservazioni so Fossili Nummulitici. Riv. ital. Paleont., 35, fasc. i-n: 1-21, pis.
i-3-
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U.S. geol. Surv., 260-X : 799-861, pis. 255-264.
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landisch oost-indie. Wet. Meded. Dienst. Mijnb. Ned.-Oost Indie, 6 : 3-31.
WAYLAND, E. J. & DAVIES, A. M. The Miocene of Ceylon. Quart. Jl. geol. Soc. Land., 79 : 577-
602, pis. 28-9.
PLATE i
Austrotrillina astnariensis sp. nov.
All x 50 approximately
FIG. i. B form, P3943O. Kirkuk Well 56. Henson colln.
FIG. 2. A form, P^66y. Bajawan limestone, Kirkuk. Smout & Eames colln.
FIG. 3. A form, ¥39647. Kirkuk Well 56, Henson colln. (Figs. 2, 3 = A. howchini sensu
Smout & Eames 1958).
FIG. 4. Off-centre, axial section, P^ujg. Sample J.T.P.4943, Kuh e Pataq, Luristan.
Oligocene.
FIG. 5. Holotype, P47578. Sample J.T.P.4943, Kuh e Pataq, Luristan, Oligocene.
FIG. 6. Off-centre, transve rsesection, P4758o. Sample J.T.P^Sgo Kuh e Pataq, Middle
Oligocene.
FIG. 7. A form, P4758i. Kirkuk Well K93, core 2, 2655 ft. 3 in. Ex. I.P.C. colln.
FIG. 8. A form, ¥47582. Gach Saran Well 6, 4132-33 ft. Asmari limestone, Iran.
FIGS. 9, 10. A forms, ?47583. Kirkuk Well Ki4, 2793-2808 ft. Ex. I.P.C. colln.
FIG. II. A form, P47584. Kirkuk Well Kg3, core 2, 2655 ft. 3 in. Ex. I.P.C. colln.
FIG. 12. B form. P47585. Gach Saran Well 6, 4135-36 ft., Asmari limestone, Iran.
Bull. BY. Mus. nat. Hist. (Geol.) 16, 2
PLATE i
\2
GEOL. 1 6. 2
PLATE 2
Austrotrillina howchini (Schlumberger)
All from the Pata limestone- drill hole P.Q. 2, 273-75 ft., Chowilla Dam site, South Australia.
Lower Miocene (Bairnsdalian). Ex. Geol. Surv. S. Australia collections.
FIGS, i, 2. P47586. (i) External view of test x 35 ; (2) portion of wall more highly magnified
showing finely pitted outer surface and sub-surface reticulation. See also PL 6, fig. 7.
FIG. 3. Transverse section of A form, X48, P47587.
FIG. 4. Transverse section of a more inflated A form, x 50, P47588.
FIGS. 5, 7. Decorticated A form, P475QO (cf. Fig. i). Most specimens of Austrotrillina are
found in this condition : (5) x 35 : (7) same specimen x 50.
FIG. 6. A form, P4758g. Axial section of a specimen which closely resembled fig. i externally.
For B form see Plate 6.
Bull. Br. Mus. nat. Hist. (Geol.) 16, 2
PLATE 3
FIG. i. Austrotrillina paucialveolata. Syntype X48, P4o68i ; Kirkuk Well No. 14,
Oligocene. Probably a B form.
FIG. 2. A. paucialveolata. A form, x 50, P4759I ; Kirkuk Well 14, 2828-53 ft., Oligocene.
FIG. 3. A. paucialveolata. A form, x 50, P40344 ; Kirkuk Well 14, 2828-53 ft., Oligocene.
FIG. 4. A form, x 50, P4o68i (syntype) : Kirkuk Well 14.
FIGS. 5, 6. A. paucialveolata. A form, Oligocene of Moratalla, Spain (= A. howchini of
Hottinger 1963) (5) x 55 ; (6) x 50. Deposited in the Naturhistorisch.es Museum collections,
Basle.
FIG. 7. A. cf. striata x 50. Lower Coralline limestone, Malta, Brt. Petrol. Co., Colin.
FIG. 8. A. striata, x 50. Wall partly destroyed by recrystallization. This specimen is
indistinguishable from A. paucialveolata and is only determinable as A. striata from associated
individuals. Tagpochau limestone, Saipan. U.S.G.S. colln., sample No. MSB 260.
FIG. 9. A. striata/ howchini x 50. Bikini drill hole 2B 2038^-48 ft. This is one of the
specimens figured by Cole (1954) as A. howchini and refigured in the Treatise (1964, fig. 362-8)
under the same name. It is, in fact, intermediate between A . howchini and A . striata. U.S.N.M.
Colln.
Bull. Br. Mus. nat. Hist. (Geol.) 16, 2
PLATE 3
PLATE 4
Austrotrillina striata Todd & Post
All x 50 unless otherwise stated
FIGS. 1-3. A forms ^47592, P47593) from Eniwetok drill hole E-i, 1895-925 ft. Figs, i, 2
are of the same individual. Fig. 2 shows the external appearance of the test when immersed in
oil ; decorticated specimens also look like this.
FIGS. 4, 7. A forms from Eniwetok drill hole E-i, 1925-55 ft. U.S.N.M. colln. (4) trans-
verse section, (7) longitudinal section. Note that the alveolar structure is not visible in the
early chambers.
FIGS. 5, 9, 11-13. All from Eniwetok drill hole E-i, 1925-55 ft. (5) P47594, A form; (9)
surface view of typical specimen showing fine striae, P^j^gj ; (n) longitudinal section through
A form; P47599; (12) wall of terminal chamber viewed from inside, X56, P476oo; (13) A form,
terminal chamber broken off — note ' step ', P476oi.
FIGS. 6, 10. A forms from Eniwetok drill hole E-i, 1996^-2007 ft., ?47595 & 47598.
All ex. U.S.G.S. collection.
FIG. 8. A form (P47596) from Bikini drill hole 2B, 2049-2059^ ft. Topotype. Ex U.S.G.S.
colln.
Bull. BY, Mus. nat. Hist. (Geol.) 16, 2
PLATE 4
PLATE 5
The figures on this plate illustrate the difficulty in determining specimens from certain Indo-
Pacific (Upper Te) limestones where transitional forms between A . striata and A . howchini occur,
or where the range of variation of A. striata overlaps that of A. asmariensis.
FIG. i. Austrotrillina sp. X5o, P46525. Intermediate between A. striata and A. how-
chini. Upper Te, Melinau limestone, Sarawak.
FIG. 2. A. striata X52, P4&526. Upper Te, Melinau limestone, Sarawak.
FIG. 3. A. striata X5O, P^6^22. Lower Te, Melinau limestone, Sarawak.
FIG. 4. A. cf. howchini x 50, P4&524. Upper Te, Melinau limestone, Sarawak.
FIGS. 5, ii. A. cf. howchini x 50, P^j6o2, P4y6o6. Primitive forms from the Tagpochau
limestone, Saipan. Sample No. MSB 413. U.S.G.S. colln.
FIGS. 6, 7. Austrotrillina sp. X5o. Tagpochau limestone, Saipan U.S.G.S. colln.
Sample No. MSB 397, Lower Te. These specimens are not strictly determinable In some
respects they resemble A. asmariensis, in others A. striata / 'howchini (6) P476O3 ; (7) P476O4-
FIG. 8. Austrotrillina sp. X5O. Tagpochau limestone, Saipan, Sample No. MSB 403,
U.S.G.S. colln. Intermediate between A. striata and A. howchini.
FIG. 9. A. cf. striata Todd & Post, B form, x 50, P476o5. Tagpochau limestone, Saipan.
Ex Sample No. 6397, U.S.G.S. colln.
FIG. 10. A. cf . howchini x 50. Part of wall of a specimen from the Tagpochau limestone,
Saipan. Sample No. MSB 388, U.S.G.S. colln.
Bull. Br. Mus. not. Hist. (Geol.) 16, 2
PLATE 5
PLATE 6
FIG. i. Austrotrillina howchini, A form X5O. Lower Chake beds, south end of Funzi
Island, Pemba Island, Tanzania. PzzS^S.
FIGS. 2, 4, 5. A. howchini. All x 50. ¥47607 (ex. P29878). All from the Lower Miocene
of the Malabar coast, Cochin, Travancore, India. Associated with Taberina malabavica (Carter)
for which this is the type locality : Carter collection.
FIG. 3. A. howchini. B form, x/fo, ¥47608. Pata limestone, Chowilla Dam site, South
Australia. Lower Miocene (Lower Tf).
FIGS. 6, 8. A. brunni. Re-illustration of two of Marie's types : X 35 and x 50 approx.
FIG. 7. A. howchini. Stereoscan electron microscope photograph showing surface pits.
The subsurface reticulation is no longer visible as the specimen is coated with a fine gold film.
Same individual as PI. 2, figs, i, 2. x 750, KV 20.
FIG. 9. A. striata. Stereoscan electron microscope photograph showing surface striae and
pits. Bikini Well 2b, 2091-2102 feet. P476O9 x 750, KV2O. Note that the pits are smaller
than in A. howchini.
Bull. Br. Mus. nat. Hist. (Geol.) 16, 2
PLATE 6
PRINTED IN GREAT BRITAIN
BY ADLARD & SON LIMITED
BARTHOLOMEW PRESS, DORKING
BRITISH NEOCOMIAN
RHYNCHONELLOID BRACHIOPc
E. F. OWEN
and
R. G. THURRELL
BULLETIN OF
THE BRITISH MUSEUM (NATURAL HISTORY)
GEOLOGY Vol. 16 No. 3
LONDON: 1968
BRITISH NEOCOMIAN RHYNCHONELLOID L20FEB
••
BRACHIOPODS ^
K\
BY
ELLIS FREDERIC OWEN
British Museum (Natural History)
and
REGINALD GEORGE THURRELL
Institute of Geological Sciences
Pp. 99-123; 4 Plates, 8 Text-figures
BULLETIN OF
THE BRITISH MUSEUM (NATURAL HISTORY)
GEOLOGY Vol. 16 No. 3
LONDON : 1968
THE BULLETIN OF THE BRITISH MUSEUM
(NATURAL HISTORY), instituted in 1949, is
issued in five series corresponding to the Departments
of the Museum, and an Historical series.
Parts will appear at irregular intervals as they become
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In 1965 a separate supplementary series of longer
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Scientific Periodicals.
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Bull. Br. Mus. nat. Hist. (GeoL).
© Trustees of the British Museum (Natural History) 1968
TRUSTEES OF
THE BRITISH MUSEUM (NATURAL HISTORY)
Issued 20 February, 1968 Price £i is.
BRITISH NEOCOMIAN RHYNCHONELLOID
BRACHIOPODS
By E. F. OWEN & R. G. THURRELL
CONTENTS
Page
I. INTRODUCTION ......... 101
II. STRATIGRAPHICAL SUMMARY ....... 102
III. SYSTEMATIC DESCRIPTIONS ....... 108
Family RHYNCHONELLIDAE ....... 108
Subfamily CYCLOTHYRIDINAE Makridin ..... 108
Lamellaerhynchia rostriformis (Roemer) . . . . 108
Lamellaerhynchia walkeri (Davidson) . . . . . 113
Lamellaerhynchia walkeri claxbyensis subsp. n. . . . 114
Lamellaerhynchia rawsoni sp. n. . . . . . . 116
Lamellaerhynchia julenia sp. n. . . . . . . 116
Lamellaerhynchia cf. picteti Burri . . . . . 117
Rhynchonella parkhillensis sp. n. . . . . . 117
Rhynchonella speetonensis Davidson . . . . . ng
IV. CONCLUSIONS .......... 121
V. REFERENCES .......... 122
SYNOPSIS
A short stratigraphical account is given of the Lower Cretaceous, Neocomian beds of the
southern part of the Lincolnshire Wolds. The Rhynchonellidae collected from these strata
and beds of similar age in the northern Wolds, and from the Speeton Clay of Yorkshire are
systematically described and compared with the corresponding fauna of the Brunswick and
Hanover districts of north-west Germany, and also with faunas described from Neocomian
horizons in Switzerland.
INTRODUCTION
IT was agreed at the Colloquium on the Lower Cretaceous held at Lyon, France
in 1963 (p. 832) that the term Neocomian should not be used as a stage name, but
that it should, perhaps, be preserved for a group of stages. It was further agreed
that the term should be limited to represent three stages in the Lower Cretaceous
namely, Berriasian, Valanginian and Hauterivian, and that the Barremian should
be regarded as a separate stage midway between the top of the Hauterivian and
the base of the Aptian.
It is difficult when dealing with older classifications and groupings of beds to be
precise about the geological age. For this reason, and because the term Lower
Cretaceous has a somewhat broader connotation, the term Neocomian as used in
this paper sometimes includes reference to the Fulletby beds, generally regarded
as of Lower Barremian age.
The material on which this paper is based was collected during the course of
field surveys of the Lower Cretaceous rocks of the Lincolnshire Wolds, and from
the cliff section at Speeton, Yorkshire. The descriptions of the formations in the
GEOL. l6, 3. IO
102 BRITISH NEOCOMIAN
southern Wolds are taken from a thesis submitted and approved in 1957 for the
degree of Ph.D. of London University by one of the authors (R.G.T.). Many of
the species of Rhynchonellidae described here from the Speeton Clay and from
the Claxby Beds of Nettleton, Lincolnshire, were collected by Dr. P. Rawson during
his study of the northern Wolds for a thesis submitted and approved for the Ph.D.
degree of Hull University in 1967.
Brachiopods appear sporadically throughout the British Neocomian but occur
most frequently in the C6-D2 Beds of Swinnerton at Speeton and in the condensed
sequence of the Spilsby and Claxby series southeast of Nettleton. All the forms
described here are from three main sources : Beds C6, Dj_2 of Speeton Cliff, York-
shire; Claxby Beds at Nettleton, Lincolnshire [110980] ; and the Roach Stone of the
Fulletby Beds at Cawkwell [280880], Belchford [290750] and Dalby Park [410700],
Lincolnshire. All National Grid references quoted fall within the 100 km. square TF.
Although the area occupied by the outcrop of the lower Cretaceous rocks in
Lincolnshire far exceeds that of the Speeton Clay in Yorkshire, they have attracted
much less attention. They are generally poorly exposed and even when brick-clay,
iron-ore and building stone were being dug during the last century, useful occur-
rences were few and far between. Efforts to correlate the strata below the Red
Chalk were at first attempted on rather tenuous geological evidence. Judd (1870)
was the first to employ palaeontological methods, using the ammonites to compare
the English facies with rocks at localities he had visited in Europe. A zonal standard
of reference had not been established in any region at that time, but later research,
mainly at Speeton, resulted in the publication of a zonal scheme based on the
belemnites (Lamplugh 1889, 1924), which has remained in use until the present
with only minor modifications (see Swinnerton 1936-55).
Lamplugh (1896 : 191-293) showed that the Speeton subdivisions were also
recognizable in the Lincolnshire Neocomian, but other workers have preferred the
more precise correlations afforded by the ammonite assemblages. Spath (1924)
published a comprehensive system of zones for the Lower Cretaceous. Swinnerton
(1935) recorded the presence of two additional ammonite faunas in the bottom
three feet of the Spilsby Sandstone at Fordington Pumping Station [416714] Lin-
colnshire and added considerably to knowledge of the stratigraphy and faunas of
the Neocomian of the southern Wolds. He proposed (1935, 1936) the lithological
subdivisions adopted here, which embody the nomenclature originally proposed
in the Geological Survey's memoir (Jukes-Browne 1887) but with further subdivi-
sions inserted and the system of grouping the formations under geological headings
extended. In the absence of borehole data, the thicknesses quoted in the following
table have been assessed from field mapping, supported by aneroid traverses with
allowances made for the effects of superficial movements, structural complications
and facies changes.
The most complete and lithologically variable development of the Lower Creta-
ceous rocks crops out in the southern Lincolnshire Wolds between Fulletby and
Spilsby. The general north-westward attenuation of the strata may be attributed
to continued uplift of the Market Weighton Axis during Neocomian times with the
consequent development of additional non-sequences and changes of facies towards
RHYNCHONELLOID BRACHIOPODS
TABLE i
103
Langton Series : Carstone Beds
Tealby Series : Fulletby Beds
Tealby Beds
Claxby Beds
Spilsby Series : Spilsby Beds
Carstone Grit
Carstone Sands and Clay
Sutterby Marl
Upper Roach
Roach Stone
Lower Roach
Upper Tealby Clay
Tealby Limestone
Lower Tealby Clay
Upper Claxby Ironstone
Hundleby Clay
Lower Claxby Ironstone
Ferruginous Grit
Glauconitic Sands
Basement Beds
Estimated thickness in feet
North
Willingham Belchford Dalby
33
40
70 +
34
60
35
70
Go
that area. A number of interpretations of the detailed interrelations and variations
of the formations in Lincolnshire have been published (e.g. Wilson 1948 : 54,
Swinnerton & Kent 1949 : 73). From the present six-inch survey, the base of the
Carstone Grit appears to overstep northwards all formations successively from the
Sutterby Marl down to the base of the Upper Tealby Clay, as shown in Fig. i.
Thinning and change of facies within the Fulletby Beds in the same direction
results in the disappearance of the Roach Stone north of Scamblesby [275788].
For the same reasons, the Hundleby Clay facies diminishes north-westwards and
cannot be traced farther north than Belchford.
The typical lithologies of the strata from which many of the Rhynchonellidae
described in this paper have been obtained are outlined below.
Claxby Beds
These beds, named from their well-known occurrence in the old ironstone workings
[112963] near Claxby-by-Caister, were first described by Judd (1867 : 245; 1870 :
329) although Dikes & Lee (1837) had previously noticed a " ferruginous band "
. . . at the . . . " top of the Green Sandstone" [ = Spilsby Sandstone] at Nettleton.
Ferruginous and non-ferruginous lithofacies are distinguishable in Lincolnshire.
The former is present in the northern and central Wolds as the Claxby Ironstone;
south-east of Belchford [290750] both facies have been mapped, the non-ferruginous
Hundleby Clay being recognizable as pale, purplish-grey, silty clay which splits
the ironstone at about the middle and appears progressively to replace the lower
part, until in the extreme south-east of the Wolds it comes to rest directly upon
the Ferruginous Grit of the Spilsby Beds.
From a thickness of fourteen feet at Nettleton, there is no appreciable south-
easterly thickening of the Claxby Beds at outcrop for twenty miles. At Harrington
[365720] twenty-three feet are estimated to be present and almost thirty feet at
io4
BRITISH NEOCOMIAN
FLAMBOROUGH
HEAD
FIG. i. Outcrop and sub-drift occurrences of the Lower Cretaceous rocks
in east Lincolnshire and east Yorkshire.
RHYNCHONELLOID BRACHIOPODS 105
Partney [410680]. The Hundleby Clay is estimated to be up to five feet thick at
Belchford, fifteen feet at Hundleby [385640] and eighteen feet at East Keal [375645].
The ironstone fades is characterized by the ubiquitous presence, in varying con-
centrations, of oolitic iron ore embedded in pale-grey to dark-brown, ferruginous
silty clays with pink or cream, calcareous, siltstone bands at some levels. These
harder bands contain much less oolitic material than the clays, but both rocks
may be hardened and secondarily enriched by ferruginous impregnation and by
the oxidation of iron salts to limonitic material which occurs commonly as flaky
aggregations in irregular veins and as encrusting " iron pan ".
Glauconite is rare but polished well-rounded pebbles of chert and subangular
quartz grit are found, especially about the middle and near the base of the ironstone.
Beds of round phosphatic nodules up to four inches across may contain moulds
of ammonites, belemnites and " steinkerns " of bivalves. These, together with
frequent evidence of contemporaneous erosion, such as the presence of thin beds
of broken shells and aggregations of broken and abraded ooliths resting on churned,
uneven surfaces suggest that a number of minor non-sequences may exist. Clusters
of brachiopods are found more commonly in the oolitic clayey seams than in associ-
ation with other faunal elements, which appear to have flourished more persistently
in the silty environments.
The Hundleby Clay fades normally comprises pale purplish-grey, mottled-brown,
silty clay. It tends to become more arenaceous towards the top with yellow-
stained shaly micaceous partings. At the type locality, near Spilsby, lenses of
coarse, black, pyritous grit and others of white sand up to two inches thick and
twelve inches long are present just below the Upper Ironstone, interbedded with
irregular bands of decalcified, concretionary, buff-coloured siltstone nodules com-
monly traversed by irregular fractures infilled by ochreous ferruginous matter.
At lower levels the Hundleby Clay characteristically contains less silt and, between
Belchford and Hundleby itself, the whole thickness of the formation comprises
unctuous, plastic clay wherever it is thick enough to be separately mapped. The
sparse macrofauna appears to be devoid of brachiopods.
The Futtetby Beds
Formerly referred to by the Geological Survey as " The Roach " (Jukes-Browne
1887 : 19), the Fulletby Beds were first so called by Swinnerton (1935) from their
obvious presence in the cliff-like feature which distinguishes the northern part of
Fulletby Hill [300750], the type locality.
The formation is predominantly clayey, essentially ferruginous but rarely glauco-
nitic, so that it is readily distinguishable in the Lower Cretaceous sequence. Ex-
posures, though few, are usually of the Roach Stone. Characteristically reddish-
brown clay loams are developed everywhere on these beds.
The Fulletby Beds were subdivided by Swinnerton (1935 : 4) as follows:
Estimated thickness in feet
Fulletby /Belchford Tetford/Harrington
Upper Roach 10-15 J5
Roach Stone 4-6 15
Lower Roach 15-20 30
io6 BRITISH NEOCOMIAN
Of all the Lower Cretaceous rocks which crop out in Lincolnshire, these are prob-
ably the most variable in thickness and lithology. The clay or silty-clay matrix
is commonly dark grey, though it may weather to brown and bright reddish-brown
where concentrations of iron ore are particularly high. Grit grains and small
rounded (lydite) pebbles are disseminated throughout. Churned horizons, as if
brought about by contemporaneous erosion or by organisms, have been observed
only rarely.
The Roach Stone crops out just above the middle of the Fulletby Beds, where the
predominantly clayey sequence rapidly becomes sandy, somewhat less ferruginous
and markedly more calcareous. At a higher level, the arenaceous nature of the
Roach Stone is continued into the heavily ferruginous, silty Upper Roach.
The Roach Stone was originally described from the borehole at Alford (Swinnerton
1935 : 10) as a " hard calcreted ferruginous sandstone " approximately twelve feet
thick. This description accords well with that given here for the sandstone facies
at outcrop. The sandstone, however, is exposed infrequently and it is the ironstone
facies which is seen at a number of localities over the whole area, and often it is the
sole representative of the Roach Stone, especially in the ground northwest of Fulletby.
These facts, especially the last, may suggest that the " ironstone " facies represents
a lateral lithological development of the sandstone facies towards the northwest,
as well as the indurated equivalent of those Roach beds which lie immediately above
and below it in the southern part of the Lincolnshire Wolds. Accordingly, for
practical reasons, the Roach Stone is here taken to include all the coherent strata
at about the middle of the Fulletby Beds which give rise to mappable lithological
and topographical features, irrespective of the previous lithological definition.
The ferruginous content of these beds is predominantly in the form of black or
dark-brown polished ooliths or limonite, although there is also a subordinate amount
of amorphous and flaky ore, most of which appears to be secondary. The distri-
bution of the indigenous limonite varies greatly; at the outcrop there is very little
oolitic material in the Roach Stone or at the extreme base of the Fulletby Beds,
but passing upwards in the Lower Roach, the oolitic content gradually increases
to a maximum concentration in a bed just below the Roach Stone as defined by
Swinnerton (1935) in boreholes. This rock is little more than a compact agglomera-
tion of ooliths with subordinate silty-clay matrix which has sometimes been made
coherent at the outcrop by secondary " iron-pan " deposits, but which is more
usually friable, and less sandy than Roach Stone. Above the Roach Stone the
concentration of oolitic iron ore is high but it appears to decrease, and the fraction
of the variegated clay and silty-clay to increase inversely, as the beds are traced
upwards towards the base of the Sutterby Marl. At the base of the marl, however,
the Upper Roach is again strongly oolitic in some localities (Cawkwell and Sutterby
[385720]) but predominantly clayey at others (Dalby Park).
The Roach Stone occurs as two fairly distinct types; an earthy limonite rock
and a calcareous sandstone. In the field, both rock types are recognizable in many
small exposures, but it is not clear what the inter-relationship of these facies is,
either in time or space. Both rock types may be examined in the same general area
and both may be much disguised and hardened by secondary " iron-pan " deposits.
RHYNCHONELLOID BRACHIOPODS
107
GEOL. 16, 3.
io8 BRITISH NEOCOMIAN
The sandstone fades is a hard fine-grained, yellowish-brown, evenly bedded silt-
stone or sandstone cemented by a ferruginous and calcareous ground-mass enclosing
scattered grit grains and a few limonite ooliths which are normally evenly distributed
but may be more rarely confined to certain layers. The sandstone weathers along
moderately strong, rectangular joints into flaggy fragments up to one foot square
by about two inches thick, but more massive blocks can be picked up in ploughed
fields. Fossils are extremely rare in this facies and no well preserved examples
have been collected, but thin sections reveal a limited microfauna.
The ironstone facies is a soft, earthy rock with less sandy material and more oolitic
limonite disseminated throughout than in the sandstone facies. It is also much
more variable in lithology: primary calcitic cement may be unevenly replaced by
tenaceous "iron-pan " and ferruginous veining which makes the collection and
development of the sparse shelly fauna a tedious process ; secondary calcite crystals
may be present in cavities in the rock and encrust exposed blocks. With diminish-
ing arenaceous content the ironstone facies tends to become even more strongly
oolitic, softer, and to contain thin bands of broken shell debris, including disarticu-
lated valves of brachiopods. This rock, when weathered, produces reddish-brown
heavily ferruginous clayey loam, the true " roach " of the countryman, containing
soft, crumbling boulders of ironstone from which a limited fauna of bivalves, belem-
nites and brachiopods has been recovered. In the Belchford-Fulletby districts,
this facies of the Roach Stone also contain fragments of woody debris and peculiar
root-like concretions (" fucoids ") made of compact, silty ore.
Hitherto the Fulletby Beds have been regarded as being poorly fossiliferous, and
indeed very few fossil genera have been recorded specifically from this subdivision
of the Tealby Series. Of a number of brachiopods collected during the field survey,
the Rhynchonellidae are now recorded and described for the first time from the
English boreal Cretaceous. The brachiopod fauna from the Claxby Ironstone was
described in part by Davidson (1874), and a revision of the Rhynchonellidae des-
cribed by him is given here, with additional descriptions of species from a similar
horizon in the Speeton Clay and from the Hanover district of north-west Germany.
SYSTEMATIC DESCRIPTIONS
Superfamily RHYNGHONELLAGEA Schuchert 1896
Family RHYNGHONELLIDAE Gray 1848
Subfamily GYCLOTHYRIDINAE Makridin 1955
Genus LAMELLAERHYNCHIA Burri 1953
Lamellaerhynchia rostriformis (Roemer)
(PL i, figs. 1-6; PL 2, figs. 1-9; PL 3, fig. 2; Text-figs. 3, 4)
1836 Terebratula rostriformis Roemer : 40, pi. 2, fig. 22.
1839 Terebratula multiformis Roemer : 19, pi. 18, fig. 8.
1839 Terebratula rostralina Roemer : 20, pi. 18, fig. 7.
1841 Terebratula multiformis Roemer; Roemer : 37.
RHYNCHONELLOID BRACHIOPODS 109
1842 Terebratula rostralina & rostrata Roemer; Leymerie : pi. 15, fig. n.
1863 Rhynchonella multiformis (Roemer); de Loriol : 113, pi. 15, fig. 23.
1864 " Rhynchonella depressa Credner " (in part); Credner : 549, pi. 18, figs. 5-12.
1871 Terebratula depressa Quenstedt (non Sowerby, 1825); Quenstedt : 155, pi. 41, figs. 2, 6-10.
1872 Rhynchonella multiformis (Roemer); Pictet : 10, pi. 195, figs. 5-8.
1913 Rhynchonella multiformis (Roemer); Jacob & Fallot : 52, pi. 7, figs. 5-7.
1953 Lamellaerhynchia multiformis (Roemer); Burri : 275, fig. 2.
1956 Lamellaerhynchia rostriformis (Roemer); Burri : 652, pi. 7, figs, i, 2, pi. 10, fig. 3.
DESCRIPTION. Biconvex Lamellaerhynchia varying from about 18-24 mm- l°ng>
20-26 mm. wide and 12-15 mm. thick with a low median fold on the brachial valve
and a correspondingly shallow sulcus in the pedicle valve. In some mature forms
there is a marked tendency for the shell to become trilobate where the median fold
is poorly developed. The uniplicate anterior margin shows some tendency to
asymmetry and marginal thickening. The suberect beak is bordered by well-
marked beak-ridges defining a broad, extensive interarea. Outward projections of
the conjunct deltidial plates extend posteriorly and encircle a large foramen.
In outline the shell varies from subcircular to elongate-oval to broadly triangular.
The umbo varies from short and massive to produced and sharp with incurvature
of the beak. In the typical form, the ornament consists of twenty to twenty-four
sharply defined, strong, radiating, non-bifurcating ribs on each valve with four to
five on the fold and a similar number in the sulcus. In some of the variants the
number of costae on each valve depends on the type of rib ; some having fine, more
rounded costae while others have more numerous but narrower, sharp ribs.
Internal characters. In the original description of the genus Lamellaerhynchia
Burri (1953 : 276, fig. 3), included a series of thirteen transverse serial sections
through the umbo of a specimen under the specific name of L. multiformis, from
the Hilsconglomerat of Berklingen, Brunswick, north-west Germany, and added a
further single section of another specimen from the Lower Hauterivian of Bachbett
des Arnon, Switzerland. In a subsequent description of the genus Burri (1956 :
652, 655), correctly quoting the valid name for the type-species of the genus as
Terebratula rostriformis Roemer, included a further series of transverse sections of
a specimen from Bachbett des Arnon, Switzerland.
Comparison of the series of transverse sections made by the authors from topotype
material, and those made and published by Burri reveals fundamental differences
which are recorded here. Although in general outline the umbonal cavities appear
similar, the main differences lie in the distal ends of the hinge-plates which, in the
specimen figured by Burri (1953 : 276) from Berklingen, are seen to have a concave
dorsal surface and are, in the broadest sense, Y-shaped. The Swiss specimen
which Burri (1956 : 655) subsequently figured is shown to have gently curving
hinge-plates with no discernible division at the distal ends. The fourteenth section
in the series showing the posterior ends of the crura is taken from the same specimen
in each case, as admitted by Burri in the legend.
From this discrepancy in the description of the internal structure of Lamellaerhyn-
chia rostriformis it must be concluded that Burri does not regard the shape of the
hinge-plates as being of diagnostic importance, an assumption confirmed by his
description of the genus which bears only a brief reference to that structure. The
BRITISH NEOCOMIAN
writers, however, do not share Burri's view and include here a series of transverse
serial sections (Text-fig. 3) of a specimen of L. rostriformis from Roemer's type
locality of Elligser Brink, near Hanover, north-west Germany. It will be seen
from this series that the dorsal surfaces of the distal ends of the hinge-plates are
OO
o-4 \jl 0-6 l£^jT
0-3
FIG. 3. A series of thirteen transverse serial sections through the umbo of a specimen of
Lamellaerhynchia rostriformis (Roemer) from the Neocomian of the type locality at
Elligser Brink, Hanover, Germany. 6.35702. X2. Numerals denote distance in
millimetres between each section.
concave or broadly Y-shaped (sections 8-10) and are, in fact, similar to those shown
in Burri's original series (1953 : 276) from Berklingen. It may also be seen that
the extreme posterior ends of the crura do not terminate in the manner of Burri's
Swiss specimen i.e. acutely concave or U-shaped with the concave surface directed
towards the floor of the dorsal valve. Instead they tend to narrow anteriorly,
curving abruptly anteriorly with their concave surface both dorsally and ventrally
directed. This stage is regarded as characteristic of L. rostriformis and may even
be confined to this species since it is not shown in any of the transverse sections of
other species of Lamellaerhynchia.
A specimen from Gros Vahlberg, north-west Germany (Text-fig. 4), preserved in
a crystalline limestone matrix, shows this feature and once again demonstrates
the concave surface of the ends of the hinge-plates. It should be noted that the
dorsal median septum in this specimen appears more strongly developed and this
may prove to be a variable character.
NEOTYPE. Terebratula multiformis Roemer 1839 is a synonym of the earlier
T. rostriformis Roemer 1836, which therefore has priority and must be used even
RHYNCHONELLOID BRACHIOPODS in
though there is no evidence that Roemer ever used the name subsequent to 1836.
The type material was housed in the Roemer Collection at the Hildersheim Museum,
north-west Germany which was damaged and partly destroyed during the war
(1939-45). In order to re-establish the species as Lamellaerhynchia rostriformis
(Roemer), Burri (1956 : 653), selected a neotype from the remainder of the Roemer
collection. This specimen, which he figured (Burri 1956, pi. 7, fig. i a-d) is in the
Roemer-Museum at Hildersheim, registered number ySia. It is stated to have
been collected from the ' ' Hilston ' (Astieria-zone = oberstes Valanginien oder
Noricuszone = unterstes Hauterivien) " of Elligser Brink, near Hanover.
REMARKS. Roemer's original definition of Terebratula multiformis (1839 : T9>
pi. 18, fig. 8) was so loosely expressed that it has hitherto been possible to include in
it a large number of variable forms which, although they are doubtlessly closely
interrelated genetically, may nevertheless be separated generically with advantage.
Burri has found it practicable to differentiate between certain of these forms which
are morphologically distinct in Switzerland and south-east France. He points out,
however, that in north-west Germany the individual species of the genus Lamel-
laerhynchia are less distinct so that the amount of morphological variation produces
transitional forms which cannot be assigned with certainty to any of the established
species. This observation is reinforced by our experience with the comparatively
few specimens collected from Lincolnshire and Yorkshire.
With such a variable species as L. rostriformis, and with so little material available
from widespread localities, it is impossible to give any statistical data which would
be of significance in determining the true morphological characteristics. Specimens
collected from limestone localities, although in the main smaller, appear identical
in every respect with those collected from the clays. Specimens collected from the
Speeton Clay are comparatively rare, so a comparison has been made between
limestone forms from Nettleton and those in a softer, more argillaceous, matrix
from the " Elligser Brink Schiste " in the Hanover district of Germany. Likewise,
specimens collected from limestone localities in Germany, such as Gros Vahlberg
have been compared with similar forms from Nettleton in this country. In each
case there has been perfect matching of both the typical form and intermediate
variants.
From the foregoing description it may appear that such morphological differences
in thickness, sharpness and number of costae, overall outline, produced beak and
relative size might constitute an argument in favour of taxonomic separation, but
no stratigraphical advantage is yet apparent. The variants described as having
more numerous rounded costae, more produced beaks and more triangular outline
could, perhaps, be referred to a subspecies, but the paucity of well-collected material
from the Neocomian in this country and in north-west Germany makes such a
separation difficult.
Burri (1956 : 695) does not record the geological range of this species, but it
seems almost certain that the earliest record is from the Upper Valanginian and
the latest from the top of the Hauterivian.
Jacob & Fallot (1913, pi. 7, figs. 5-7) figured three specimens under the name
BRITISH NEOCOMIAN
0-3
04^fcX " Vj|j^
0-3
FIG. 4. Another series of fourteen transverse serial sections through the umbo of a speci-
men of Lamellaerhynchia rostriformis (Roemer) from the Neocomian of Gros Vahlberg,
north-west Germany. The dorsal septum is shown to be more highly developed and
more persistent in this specimen. 6.35703. X2. Numerals denote distance in milli-
metres between each section.
Rhynchonella multiformis (Roemer). These resemble typical L. rostriformis, and
illustrate perfectly the breadth of variation in size and type of costation to be found
in this species. They were collected from the Upper Valanginian of the Jura Moun-
tains, Switzerland. The specimen represented by fig. 5 is similar in general outline
to extreme variants of the species collected at Gros Vahlberg, north-west Germany,
and from the Claxby Ironstone at Nettleton and figured here (PI. 2, figs. 4, 5). They
also represent the species T. rostralina which Roemer (1840, pi 18, fig. 7) briefly
described and figured from the Hils of Schandelahe and Schoppenstedt, near
RHYNCHONELLOID BRACHIOPODS 113
Hanover. This form is very often found in association with specimens which
grade into the typical form and is here considered to be a variant and, therefore,
a synonym of Lamellaerhynchia rostriformis.
Another notable variant has been found in zone C7 of the Speeton Clay and
departs from the typical form in its type of costation. The costae are less acutely
angular and less incised, giving them a more rounded appearance, but in general
outline the shell follows the same morphological pattern as the typical form. A
specimen illustrating this type of variation is figured on PI. 2, fig. 9. It is housed
in the Hull Museum and registered as 61/64/9. A similar specimen is in the private
collection of Mr. R. Clements of Hull University.
In some smaller variants the dorsal fold appears to be more highly developed,
with resulting inflation of this valve. These features are often accompanied by a
more massive, truncated umbo, slightly smaller foramen and less extensive interarea
in the ventral valve.
In spite of its variability L. rostriformis can be readily distinguished from other
species of Lamellaerhynchia, mainly by its larger dimensions, coarser angular costae
in the typical form, massive umbo and extensive interarea. As in the case of
many described species of Lamellaerhynchia, L. rostriformis has a tendency to
asymmetrical development of the anterior commissure. It also exhibits marked
growth-lines on the shell surface, a feature not particularly well developed in other
forms of the genus.
DISTRIBUTION. Apart from the English localities of Speeton, Yorkshire and
Tealby and Nettleton in Lincolnshire, the species has been collected from the Lower
Hauterivian at Auxerre, Yonne, France; Ste. Croix, Switzerland; and Schoppenstedt,
Berklingen, Delligsen, Elligser Brink and Gros Vahlberg of the Brunswick and
Hanover districts of north-west Germany.
Lamellaerhynchia walkeri (Davidson)
(PI. 4, figs. 3-8, Text-fig. 5)
1882 Rhynchonella walkeri Davidson : 68, pi. 8, fig. 33 only.
1964 " Rhynchonella " walkeri Davidson; Rudwick : 145, Text-fig. 6A.
EMENDED DIAGNOSIS. Shell subcircular to oval in outline, biconvex. Dorsal
valve inflated. Fold and sulcus broad and shallow. Twelve to fourteen coarse,
angular ribs on each valve. Umbo short, suberect. Foramen moderate to small,
hypothyrid. Deltidial plates conjunct. Beak-ridges distinct, interarea broad,
extensive.
LECTOTYPE. Davidson (1882) figured two specimens. Of these, his pi. 8, fig. 33
is a true representative of the species as it is widely known and was collected from
the Claxby Ironstone at Acre House Mine, near Claxby, Lincolnshire. The second
specimen, figured as pi. 8, fig. 34, departs from this form in ornament and outline
and is not a true L. walkeri. It is housed in the Museum of the Institute of Geological
Sciences (Geological Survey) and is registered as G.S.M. 110258. It is described
elsewhere in this paper as L. walkeri claxbyensis subsp. n.
H4 BRITISH NEOCOMIAN
The specimen selected as lectotype is, therefore, that figured by Davidson on
pi. 8, fig. 33; it is housed in the Sedgwick Museum, Cambridge and registered as
S.M.B.H40I.
Dimensions of lectotype. Length 18 mm., width 22 mm., thickness 15 mm.
EMENDED DESCRIPTION. In the early growth stages the costation, which is
characteristically angular, is already distinct. The curvature of both valves remains
costant during development, so that the convexity of the valves is regular right up
to the line of the anterior commissure in all but gerontic individuals, in which
further growth produces a flattened anterior aspect. The low median fold on the
dorsal valve and the shallow sulcus in the ventral valve both develop late and
gradually become differentiated from the flanks.
The adult shell is unequally biconvex, approaches an almost spherical outline,
and is ornamented by strongly-developed, coarse, angular ribs. There is some
variation but the typical form maintains an average length of 16 mm., width of
19 mm. and thickness of approximately 12 mm.
The dorsal valve is strongly convex, becoming increasingly gibbous in the region
of the fold which may be occupied by three or four ribs. The broad shallow sulcus
in the ventral valve usually develops two or three ribs. A well-marked growth-
line is often visible just anterior to the umbonal region, at a point approximately
2-3 mm. from the apex. Otherwise growth-lines are marginal and tend towards
lamellar development in older individuals.
Internal characters. These are consistent with those described for the type species
with the exception of a somewhat more acute deflection of the hinge-plates towards
the floor of the dorsal valve. The broad, concave ends of the radulifer crura are typical.
DISTRIBUTION. Lamellaerhynchia walkeri occurs in the Claxby Beds of Lincoln-
shire, where it is not common. It also occurs in the Neocomian of north-west
Germany. Two examples are figured here. PI. 4, figs. 7, 8 from the Hauterivian
of Elligser Brink for comparison with examples from Claxby Ironstone localities.
REMARKS. The degree of variation exhibited by this species is not great and
is confined to the coarseness and small number of ribs which are seen throughout
all stages of growth, deeply incised on the surface of each valve. The general
outline, which is subcircular in the typical form, varies only slightly, becoming
more elongate-oval in some and perhaps faintly triangular in other variants. Al-
though no other British Cretaceous species could be easily confused with L. walkeri
there are other forms which approach this species in general morphology. They
differ in their more numerous, less acutely angular ribs, less convex valves and more
highly-developed median fold on the dorsal valve.
Lamellaerhynchia walkeri claxbyensis subsp. n.
(PI. 3, figs. 3, 4)
1882 Rhynchonella walkeri Davidson : 68, pi. 8, fig. 34 only.
DIAGNOSIS. Oval to subcircular in outline. Umbo short, suberect. Foramen
small. Beak-ridges well marked; interarea broad, short. Median dorsal fold well
developed. Costa e sharp, undivided. Growth-lines marginal.
RHYNCHONELLOID BRACHIOPODS
X x
0-4
0-2
FIG. 5. Fifteen transverse serial sections through the umbo of a specimen of Lamellaerhyn-
chia walkeri (Davidson) from the Claxby Ironstone, Nettleton, Lincolnshire. The last
two sections show an enlargement ( X 5) of the distal ends of the crura. 36.44456.
X 2. Numerals denote distance in millimetres between each section.
HOLOTYPE. British Museum (Natural History) B.M. 66.42944, from the Claxby
Ironstone, Top Mines, Nettleton, Lincolnshire.
Dimensions of holotype. Length 18 mm., width 20 mm., thickness 15 mm.
DESCRIPTION. Although similar in general outline to L. walkeri the new sub-
species differs from it in having a more highly developed median fold on the dorsal
valve, a shorter umbo, and a considerably smaller foramen. The deltidial plates
are not well exposed and the broad interarea is shorter or less extensive than in
L. walkeri. The costae, typically sharp or angular, are considerably more numerous
than in L. walkeri, and average eighteen to twenty on both valves with four to five
on the fold and three to four in the sulcus. Growth-lines are confined to the margins
and often become lamellar. This development is well marked on specimens collected
from the Claxby Ironstone at Nettleton (British Museum (Natural History), BB.
GEOL. l6, 3. 12
n6 BRITISH NEOCOMIAN
42945-51). It is also noticeable in specimens from Elligser Brink in north-west
Germany, and one specimen illustrating this character is now figured (PI. 3, figs.
3a-c).
Lamellaerhynchia rawsoni sp. n.
(PL 4, figs. 11-15)
DIAGNOSIS. Small Lamellaerhynchia about 18 mm. long, 20 mm. wide and n
mm. thick when fully grown. Distinctly triangular in general outline. Median
fold well developed on dorsal valve. Umbo slightly produced, laterally excavated.
Deltidial plates conjunct, well exposed. Foramen large, circular. Interarea short,
broad, bounded by distinct permesothyrid beak-ridges. Ornament of eighteen to
twenty coarse radiating, acutely angular, deeply incised costae. Fold and sulcus
with three or four costae.
HOLOTYPE. British Museum (Natural History), B.M. 66.44424, from the Roach
Stone of Dalby Park, south Lincolnshire Wolds.
Dimensions of holotype. Length 20 mm., width 21 mm., thickness 14 mm.
PARATYPES. BB . 44421,66 . 44425, B6 . 42954 and 66 . 42955.
DESCRIPTION. Although L. rawsoni bears a strong resemblance to L. hauterivi-
ensis 6urri (1953), from the Lower Hauterivian of Switzerland, it can be readily
distinguished by its fewer costae, less well-developed median fold on the dorsal valve,
and slightly greater incurvature of the beak. It also has a well-developed growth-line
at approximately 2-4 mm. anterior to the dorsal umbo. In older individuals there
is a tendency to lamellar thickening of the margins.
Internal characters. As for the type species L. rostriformis.
DISTRIBUTION. In the same way that L. hauteriviensis 6urri is confined to the
Lower Hauterivian it would seem that L. rawsoni is a species of limited vertical
and horizontal range, being found only as a rare fossil in the Lower 6arremian,
Fulletby 6eds, of this country. It has not been identified with certainty from any
of the north German deposits though it probably exists in the 6arremian of the
Hanover area.
Lamellaerhynchia julenia sp. n.
(PI. 3, figs. 6, 7)
DIAGNOSIS. Elongate-triangular Lamellaerhynchia approximately 20 mm. long,
19 mm. wide and n mm. thick when fully grown. Produced, suberect beak,
laterally excavated. Conjunct deltidial plates well exposed. Foramen large,
circular. Acutely angular radiating costae, coarse and deeply incised. Interarea
extensive. 6eak-ridges distinct, permesothyrid. Anterior commissure with marked
tendency to asymmetry.
HOLOTYPE. 6ritish Museum (Natural History), 6.M. 66.42984, from the Lower
6arremian, Fulletby 6eds of Dalby Park, south Lincolnshire Wolds.
Dimensions of holotype. Length 21 mm., width 20 mm., thickness 15 mm.
PARATYPE. 66.42985
RHYNCHONELLOID BRACHIOPODS 117
DESCRIPTION. The outstanding features of this species are its almost equal
biconvexity and its constant eighteen to twenty costae on each valve. It is always
elongate-triangular in general outline, varying only slightly in width, with a marked
tendency to asymmetry of the anterior commissure. It bears a resemblance to
L. gillieroni (de Loriol) but differs in its coarser, more deeply incised costae and
more constantly elongate-triangular outline. It may, nevertheless, be the British
equivalent of that species, occurring in the Lower Barremian, as L. gillieroni does
in Switzerland. The morphological differences described above and the geographical
difference would seem to justify the taxonomic separation accorded here.
Internal characters. As for the type species L. rostriformis (Roemer).
DISTRIBUTION. Although Lamellaerhynchia julenia occurs only in the Lower
Barremian, Fulletby Beds in Britain, a similar form, differing only in relative size
occurs in north-west Germany at Schoppenstedt, but the exact horizon has not
been recorded. Three good examples of this species from Schoppenstedt are in
the British Museum (Natural History), B.M. 66.44460-62.
Lamellaerhynchia cf. picteti Burri
(PI. 3, figs. 8, 9)
DESCRIPTION. Acutely biconvex Lamellaerhynchia with short, massive umbo,
suberect beak and short interarea. The beak-ridges are distinct and permesothyrid.
Distinctly subcircular in general outline. Dorsal fold incipient or indistinct with
fairly shallow but broad sulcus in the ventral valve. The costae vary in number
from between twenty and thirty on each valve but there are some variants with
slightly coarser costation and a corresponding reduction in number of costae. Most
of the specimens ascribed here to this species show a tendency to asymmetry of
anterior commissure.
REMARKS. Although this species is compared here to L. picteti it is somewhat
more circular in outline than the specimens figured by Burri (1956 : pi. 8, fig. 3,
pi. 9, fig. i) but is nevertheless very similar in its type of costation, degree of con-
vexity and general appearance. None of the specimens examined exactly matches
those illustrated by Burri and it is for this reason that we have compared our species
to the original to give a somewhat broader interpretation.
DISTRIBUTION. Only three specimens of L. cf. picteti have been found in Britain
so far and these were collected from the Claxby Ironstone at Nettleton, Lincolnshire.
Genus RHYNCHONELLA Fischer 1809
Rhynchonella parkhillensis sp. n.
(PI. 4, figs. 9, 10, Text-fig. 6)
DIAGNOSIS. Species of Rhynchonella approximately 12 mm. long, 13 mm. wide,
and 9 mm. thick when fully grown. Shell biconvex, outline subcynocephalous or
n8
BRITISH NEOCOMIAN
tetrahedral. Brachial valve with angular and prominent median fold containing
two or three imbranched, simple, deeply-incised costae; sulcus with one or two
costae. Beak-ridges distinct, hypothyrid. Umbo suberect. No cardinal process.
Shallow septalium. Dental lamellae strong, subparallel. Radulifer crura.
HOLOTYPE. British Museum (Natural History), B.M. 66.42952, from the
Fulletby Beds, Roach Stone of Park Hill, Belchford, South Lincolnshire Wolds.
Nat. Grid 28907685.
Dimensions of holotype. Length 14 mm., width 14-1 mm., thickness 9 mm.
PARATYPES. 66.52953-55.
DESCRIPTION. In the early growth stages both valves are convex and smooth
to within 3-5 mm. from the umbones. At this stage the costae gradually become
discernible. A moderately deep sulcus develops and extends posteriorly with a
linguiform extension averaging 6 mm. in length. The sulcus tapers gently to form
a truncated V-shape. The lateral slopes of the fold are well marked anteriorly,
separating the high median portion from the convex flanks, and subsiding completely
where the costae arise. The number of costae on the fold varies from two to three.
In forms where two costae are developed on the fold, one costa is developed in
the sulcus. Likewise, when three costae are developed on the fold, two costae
appear in the sulcus.
FIG. 6. A series of twelve transverse serial sections through the umbo of a specimen of
Rhynchonella parkhillensis sp. nov. from the Fulletby Beds, Dalby Park. 36.44405.
X ij approx. Numerals denote distance in millimetres between each section.
Internal characters. Serial sections made from undamaged examples of this
species have been compared with a similar series from Rhynchonella loxia Fischer,
the type species of the genus, published by Ager (1957 : 8, 9). Dr. Ager has kindly
confirmed our assignment of the present species to Rhynchonella (s.s.).
REMARKS. Rhynchonella parkhillensis is named from its most prolific locality
at Park Hill, Belchford, Lincolnshire. The species is rare in the Roach Stone
over the ten miles of its outcrop. Preservation is rarely excellent, but the paucity
of natural exposures and the ferruginous nature of the matrix increase the value
of the few specimens which can be found and extracted undamaged.
Superficially, the species bears a resemblance to other species of Rhynchonella
(s.s.) as re-defined by Ager (1957), particularly to R. rouillieri Eichwald, from the
RHYNCHONELLOID BRACHIOPODS 119
Russian Upper Jurassic. Ager (1957 : 12) discussed the probable relationship of
R. rouilleri to other species of Rhynchonella and assigned it to this genus. The
species was further discussed and several subspecies described and figured by
Makridin (1964 : 113, pi. 3, figs. 2-12) from the Upper Jurassic of the Russian
Platform. Of these R. rouilleri eltonica bears a strong resemblance to R. parkhill-
ensis, but the latter can be distinguished by its more acute, triangular outline,
slightly more highly developed dorsal fold and more produced umbo. It differs
from R. loxia in having a less acute, cynocephalous outline and more produced
umbo but shares with that species the possession of fine, longitudinal striae, just
visible on the surface of the shell in well-preserved specimens. These striae are
crossed by transverse growth lines, equally faint in development, which give the
appearance of a fine reticulation over the surface of the shell.
DISTRIBUTION. Apart from the type locality at Park Hill, Belchford, specimens
have been collected form the same horizon within the Fulletby Beds at Hoe Hill,
Fulletby; Cloven Hill, South Ormsby; Dalby Park and Dalby Hill near Spilsby,
South Lincolnshire.
Rhynchonella speetonensis Davidson
(PI. 3, fig. 5, PL 4, figs, i, 2. Text-figs. 7, 8)
1836 Terebratula varians Schlotheim; Roemer : 38, II, fig. 12.
1874 Rhynchonella speetonensis Davidson : 69, pi. 8, figs. 32a-c.
EMENDED DESCRIPTION. Distinctive, subtrigonal, cynocephalous rhynchonelloid
bearing a high fold in the dorsal valve at all stages of growth. Although the species
is variable it maintains an average length of approximately 19 mm., width of 20
mm. and thickness of 16 mm. The variations are mainly confined to the width,
which may exceed the length by as much as 3-6 mm, and the height of the dorsal
fold, which is proportionately greater or more acutely arched in some variants.
No costae are developed but the shell is ornamented by numerous fine, rounded
costellae, averaging in number from sixteen to eighteen on the fold and fourteen
to sixteen in the sulcus. The costellation varies in size and, in some of the German
forms from Ellisger Brink, becomes coarse with a considerable reduction in the
number of costellae.
Internal characters. As in the case of Rhynchonella parkhillensis transverse serial
sections have been made and compared with those of Rhynchonella loxia, as figured
by Ager (1957 : 8, 9).
LECTOTYPE. Davidson (1874 : 69) described Rhynchonella speetonensis from the
Speeton Clay of Speeton, Yorkshire and illustrated his description by figuring a
specimen (1874, pi. 8, figs. 32a-c) which he said was in the collections of the Wood-
wardian Museum, Cambridge. In fact, three specimens labelled Rhynchonella
speetonensis, 6.11426, 6.11427 & 6.11428, from the Speeton Clay are housed in
the Sedgwick Museum. Of these, 6.11428 is nearest to the somewhat restored
drawing of Davidson. It is assumed that all three specimens were used by Davidson
and therefore rank as syntypes. 6.11428 is selected as lectotype; it is 15 mm.
long, 16 mm. wide and 12 mm. thick.
BRITISH NEOCOMIAN
REMARKS. The assignment of this species to Rhynchonella (s.s.) was made after
due consideration of both external and internal morphological features. R. speeton-
ensis has many internal structures in common with R. loxia, including strong,
0-1 ^m^9 0-1
FIG. 7. Thirteen transverse serial sections through the umbo of a specimen of Rhynchonella
speetonensis Davidson from the Speeton Clay, Speeton, Yorkshire. 66.44458. x ij
approx. Numerals denote distance in millimetres between each section.
slightly converging dental lamellae, shallow septalium, short dorsal median septum,
similarly-shaped hinge-plates, and radulifer crura. Externally the two species
have only two main morphological features in common, namely the general sub-
trigonal outline and the high cynocephalous median fold in the dorsal valve.
The ornament of fine costellae which distinguishes R. speetonensis does not appear
on any of the other known species of Rhynchonella. However, Ager (1957 : 6)
made special reference to faint striae observed on the shell surface of some specimens
of R. loxia, and noted that Buckman (1918), in discussing the same species, placed
sufficient emphasis on this character as to refer to it as capillation. Ager further
pointed out that similar fine striae have been seen on specimens of R. rouillieri
Eichwald from the Lower Volgian of Russia. We have also noted this feature
in our description of R. parkhillensis sp. n.
In his original description of R. speetonensis Davidson (1874 : 69) referred to the
numerous growth-lines which cross the main costellation to form a reticulate orna-
mentation. This is particularly noticeable [see PI. 3, fig. 5] in specimens from the
Speeton Clay but is less well preserved in specimens from the Claxby Ironstone.
The ornament of fine costellae and the high median fold in the dorsal valve,
together with a more highly developed or slightly produced umbo, distinguish R.
speetonensis from all other known species of Rhynchonella (s.s.).
DISTRIBUTION. The species appears to be confined to the Speeton Clay (exact
horizon uncertain), the Claxby Ironstone at Nettleton, and the Neocomian Beds
at Elligser Brink and in the Hanover district of north-west Germany.
RHYNCHONELLOID BRACHIOPODS
FIG. 8. Eleven transverse serial sections through the umbo of a specimen of Rhynchonella
speetonensis Davidson from Elligser Brink, north-west Germany. 6.11968. X2.
Numerals denote distance in millimetres between each section.
CONCLUSIONS
Since the early descriptions by Roemer (1836; 1840) the north-west German
Lower Cretaceous rhynchonelloid fauna has not been further investigated. The
paucity of well-collected material from localities of known geological age has made
any attempt to correlate the German species with the British forms from Lincoln-
shire and Yorkshire difficult. A few species have been recognized as occurring on
both sides of the North Sea and one of the most important of these is Lamellaerhyn-
chia rostriformis (Roemer). This is a variable form, but an attempt is made here
to define the broader limits of its variation and to draw a closer comparison between
the north-west German specimens and those collected from British localities. In
addition, comparison is also made between British and German forms and those
described by Burri from the Neocomian of Switzerland.
Although accepting a wide degree of variation within the limits of the species
as defined here, it is pointed out that the precise geological range of L. rostriformis
is unknown and the data obtained are based on specimens collected from Speeton
and Nettleton by Dr. R. G. Thurrell and Dr. P. Rawson, and from museum material.
It is thought that any differences in the internal characters between specimens
sectioned by the authors (Text-figs. 3, 4) and those previously published by Burri
(1953; 1956) are due, in the main, to differences in the technique of making and of
presenting drawings of transverse sections.
ACKNOWLEDGMENTS
Our thanks are due to Dr. W. T. Dean and Dr. L. R. M. Cocks of the Department
of Palaeontology, British Museum (Natural History), and to Dr. P. Rawson,
Queen Mary College, London University. The photographs are the work of Mr.
C. B. Keates to whom we also address our thanks.
122 BRITISH NEOCOMIAN
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GEOL. l6, 3.
PLATE i
a. Dorsal view. b. Lateral view. c. Anterior view.
FIGS. ia, b, c. Lamellaerhynchia rostriformis (Roemer). Neocomian, Speeton Clay,
D i Zone, Speeton, Yorkshire. Hull University Coll., H.U.C/S. 1590.
FIGS. 2a, b, c. Lamellaerhynchia rostriformis (Roemer). Neocomian, " Elligser Brink
Schist ", Elligser Brink, north-west Germany. B.M. 66.44406.
FIGS. 3a, b, c. Lamellaerhynchia rostriformis (Roemer). Neocomian, Speeton Clay,
Speeton, Yorkshire. Davidson Coll., B.M. 47262.
FIGS. 4a, b, c. Lamellaerhynchia rostriformis (Roemer). Neocomian, " Elligser Brink
Schist", Elligser Brink, north-west Germany. B.M. 66.44407.
FIGS. 5a, b, c. Lamellaerhynchia rostriformis (Roemer). Neocomian, Speeton Clay,
D2D Zone, Speeton, Yorkshire. Fletcher Coll., B.M. 66.44459.
FIGS. 6a, b, c. Lamellaerhynchia rostriformis (Roemer). Neocomian, Claxby Ironstone,
Top Mines, Nettleton, Lincolnshire. Hull University Coll., H.U.C/Rn.3O2.
All figures at natural size unless otherwise stated. 6.M. = 6ritish Museum (Natural History) .
Bull. Br, Mus. nat. Hist. (Geol.) 16, 3.
PLATE i
PLATE 2
a. Dorsal view. b. Lateral view. c. Anterior view.
FIGS, i a, b, c. Lamellaerhynchia rostriformis (Roemer). Neocomian, " Elligser Brink
Schist", Elligser Brink, north-west Germany. B.M. 66.44408.
FIGS. 2a, b, c. Lamellaerhynchia rostriformis (Roemer). Neocomian, Claxby Ironstone,
Top Mines, Nettleton, Lincolnshire. Rawson Coll., B.M. 66.44412.
FIGS. 3a, b, c. Lamellaerhynchia rostriformis (Roemer). Neocomian, Acre House Mine,
south of Nettleton, Lincolnshire. C.W. & E.V. Wright Coll., B.M. 66.44413.
FIGS. 4a, b, c. Lamellaerhynchia rostriformis (Roemer). Neocomian, Acre House Mine,
south of Nettleton, Lincolnshire. C. W. & E. V. Wright Coll., 6.M. 66.44411.
FIGS. 5a, b, c. Lamellaerhynchia rostriformis (Roemer). Neocomian, Gros Vahlberg,
north-west Germany. 6.M. 66.44410.
FIGS. 6a, b, c. Lamellaerhynchia rostriformis (Roemer). Neocomian, Claxby Ironstone,
Top Mines, Nettleton, Lincolnshire. Rawson Coll., 6.M. 66.44423.
FIGS, ya, b, c. Lamellaerhynchia rostriformis (Roemer). Neocomian, " Elligser 6rink
Schist ", Elligser 6rink, north-west Germany. 6.M. 66.9094.
FIGS. 8a, b, c. Lamellaerhynchia rostriformis (Roemer). Neocomian, Speeton Clay,
Speeton, Yorkshire. C. W. & E. V. Wright Coll., 6.M. 66.44409.
FIGS, ga, b, c. Lamellaerhynchia rostriformis (Roemer). Neocomian, Speeton Clay,
Speeton, Yorkshire. Hull Museum Coll., 61/64/9.
Bull. Br. Mus. nat. Hist. (Geol.) 16, 3.
II
PLATE 2
8a
9a
PLATE 3
a. Dorsal view. b. Lateral view. c. Anterior view.
FIGS. ia, b, c. Larnellaerhynchia cf. picteti Burri. Neocomian, Claxby Ironstone, Top
Mines, Nettleton, Lincolnshire. Rawson Coll. B.M. 66.42983.
FIGS. 2a, b, c. Larnellaerhynchia rostriformis (Roemer). Neocomian, Claxby Ironstone,
Acre House Mine, south of Nettleton, Lincolnshire. Institute of Geological Sciences Coll.,
G.S.M. 110257.
FIGS. 3a, b, c. Lamellaerhynchia walkeri claxbyensis subsp. n. Neocomian, " Elligser
Brink Schist", Elligser Brink, north-west Germany. B.M. 66.44417.
FIGS. 4a, b, c. Lamellaerhynchia walkeri claxbyensis subsp. n. Neocomian, Claxby
Ironstone, Top Mines, Nettleton, Lincolnshire. Rawson Coll., B.M. 66.42944. Holotype.
FIG. 5. Enlargement of shell surface of Rhynchonella speetonensis Davidson to show
the transverse lamellar ornament. B.M. 66.44457. Xi2approx.
FIGS. 6a, b, c. Lamellaerhynchia julenia sp. n. Lower 6arremian, Fulletby 6eds,
Dalby Park, Lincolnshire. Thurrell Coll. 6.M. 66.42985. Paratype.
FIGS. 7a, b, c. Lamellaerhynchia julenia sp. n. Lower 6arremian, Fulletby 6eds,
Dalby Park, Lincolnshire. Thurrell Coll., 6.M. 66.42984. Holotype.
FIGS. 8a, b, c. Lamellaerhynchia cf. picteti 6urri. Neocomian, Gros Vahlberg, north-
west Germany. B.M. 66.42987.
FIGS, ga, b, c. Lamellaerhynchia cf. picteti 6urri. Neocomian, Schoppenstedt, north-
west Germany. 6.M. 66.42986.
Bull. Br. Mus. nat. Hist. (Geol.) 16, 3
PLATE 4
a. Dorsal view. b. Lateral view. c. Anterior view.
FIGS. la, b, c. Rhynchonella speetonensis Davidson. Neocomian, Claxby Ironstone,
Top Mines, Nettleton, Lincolnshire. Hull Univ. Coll. H.U.C./Rn.277.
FIGS 2a, b, c. Rhynchonella speetonensis Davidson. Neocomian, " Elligser Brink
Schist", Elligser Brink, north-west Germany. Davidson Coll. B.M. 66.44419.
FIGS. 3a, b, c. Lamellaerhynchia walkeri (Davidson). Neocomian, Claxby Ironstone,
Acre House Mine, near Claxby, Lincolnshire. C. W. Wright Coll. B.M. 66.42941.
FIGS. 4a, b, c. Lamellaerhynchia walkeri (Davidson). Neocomian, Claxby Ironstone,
Top Mines, Nettleton. Rawson Coll. B.M. 66.42943.
FIGS. 5a, b, c. Lamellaerhynchia walkeri (Davidson). Neocomian, Claxby Ironstone,
Acre House Mine, near Claxby, Lincolnshire. C. W. & E. V. Wright Coll. 6.M. 66.44414.
FIGS. 6a, b, c. Lamellaerhynchia walkeri (Davidson). Neocomian, Acre House Mine.
C. W. & E. V. Wright Coll., 6.M. 66.42942.
FIGS, ya, b, c. Lamellaerhynchia walkeri (Davidson). Neocomian, " Elligser 6rink
Schist", Elligser Brink, north-west Germany. Davidson Coll. 6.M. 66.44415.
FIGS. 8a, b, c. Lamellaerhynchia walkeri (Davidson). Neocomian, " Elligser Brink
Schist", Elligser Brink, north-west Germany. Davidson Coll. B.M. 66.44416.
FIGS, ga, b, c. Rhynchonella parkhillensis sp. n. Neocomian, Lower Barremian, Fullet-
by Beds, Roach Stone, Parkhill, Lincolnshire. Thurrell Coll. B.M. 66.42952. Holotype.
FIGS. loa, b, c. Rhynchonella parkhillensis sp. n. Lower 6arremian, Fulletby 6eds,
Roach Stone, Parkhill. Thurrell Coll. 6.M. 66.42953.
FIGS, na, b, c. Lamellaerhynchia rawsoni sp. n. Neocomian, Lower 6arremian,
Fulletby 6eds, Dalby Park, Lincolnshire. Thurrell Coll. 6.M. 66.44424. Holotype.
FIGS. i2a, b, c. Lamellaerhynchia rawsoni sp. n. Neocomian, Lower 6arremian, Fullet-
by 6eds, Cawkwell, Lincolnshire. Thurrell Coll. 6.M. 66.44421.
FIGS. i3a, b, c. Lamellaerhynchia rawsoni sp. n. Lower 6arremian, Fulletby 6eds,
6elchford, Lincolnshire. Thurrell Coll. 6.M. 66.44425. Paratype.
FIGS. i4a, b, c. Lamellaerhynchia rawsoni sp. n. Lower 6arremian, Fulletby 6eds,
Dalby Park, Lincolnshire. Thurrell Coll. 6.M. 66.42954.
FIGS. i5a, b, c. Lamellaerhynchia rawsoni sp. n. Lower 6arremian, Fulletby Beds,
Dalby Park, Lincolnshire. Thurrell Coll. B.M. 66.42955.
Bull. Br. Mus. nat. Hist. (Geol.} 16, 3.
PLATE 4
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6a
6c
7c
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7a
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PRINTED IN GREAT BRITAIN
BY ADLARD & SON LIMITED
BARTHOLOMEW PRESS, DORKING
THE LOWER PALAEOZOIC
BRACHIOPOD AND TRILOBITE
FAUNAS OF ANGLESEY
D. E. B. BATES
BULLETIN OF
THE BRITISH MUSEUM (NATURAL HISTORY)
GEOLOGY Vol. 16 No. 4
LONDON: 1968
THE LOWER PALAEOZOIC BRACHIOPOD AND
TRILOBITE FAUNAS OF ANGLESEY
BY
DENIS EDWIN BEECHING BATES
University College, Aberystwyth
Pp. 125-199; 14 Plates, 2 Text-figures
BULLETIN OF
THE BRITISH MUSEUM (NATURAL HISTORY)
GEOLOGY Vol. 16 No. 4
LONDON: 1968
THE BULLETIN OF THE BRITISH MUSEUM
(NATURAL HISTORY), instituted in 1949, is
issued in five series corresponding to the Departments
of the Museum, and an Historical series.
Parts will appear at irregular intervals as they become
ready. Volumes will contain about three or four
hundred pages, and will not necessarily be completed
within one calendar year.
In 1965 a separate supplementary series of longer
papers was instituted, numbered serially for each
Department.
This paper is Vol. 16, No. 4 of the Geological
(Palaeontological] series. The abbreviated titles of
periodicals cited follow those of the World List of
Scientific Periodicals.
World List abbreviation :
Bull. Br. Mus. not. Hist. (Geol.)
Trustees of the British Museum (Natural History) 1968
TRUSTEES OF
THE BRITISH MUSEUM (NATURAL HISTORY)
Issued 19 April, 1968 Price £3
THE LOWER PALAEOZOIC BRACHIOPOD AND
TRILOBITE FAUNAS OF ANGLESEY
By D. E. B. BATES
CONTENTS
Page
I. INTRODUCTION AND ACKNOWLEDGMENTS . . . . . 129
II. SYNOPSIS OF STRATIGRAPHY . . . . . . . 130
(a) Eastern Anglesey . . . . . . . . 130
(b) The Berw Fault Complex 132
(c) The Llangwyllog Area . . . . . . . 132
(d) The Principal Area . . . . . . . 132
(e) The Gynfor Outliers . . . . . . . 137
(f) Faunal Lists ......... 138
III. FAUNAL AFFINITIES AND CORRELATIONS . . . . . 140
IV. SYSTEMATIC DESCRIPTION OF THE BRACHIOPODA .... 142
Superfamily Orthacea Woodward ..... 142
Family Hesperonomiidae Ulrich & Cooper . . . . 142
Hesperonomiella carmelensis sp. nov. . . . . 142
Monorthis typis gen. et sp. nov. . . . . . 144
Family Orthidae Woodward . . . . . . 145
Cyvtonotella sp. (i) . . . . . . . 145
Cyrtonotella sp. (2) . . . . . . . 146
Lenorthis proava (Salter) . . . . . . 146
Lenorthis sp. ........ 148
Orthambonites()} sp. (i) . . . . . . 148
Orthambonites(?) sp. (2) ...... 148
Pleurorthis costatus sp. nov. . . . . . . 149
Nicolella humilis Williams . . . . . . 150
Panderina lamellosa sp. nov. . . . . . . 151
Family Dolerorthidae Opik . . . . . . 152
Dolerorthis cf. tenuicostata Williams . . . . 152
Ptychopleurella sp. (i) . . . . . . . 152
Ptychopleurella sp. (2) . . . . . . . 153
Family Plaesiomyidae Schuchert . . . . . 154
Plaesiomys cf. robusta (Bancroft) . . . . . 154
Plaesiomys (Dinorthis] sp. . . . . . . 154
Family Plectorthidae Schuchert & Le Vene . . . 155
Plectorthis(l) sp. ........ 155
Platystrophia precedens major Williams . . . . 155
Family Skenidiidae Kozlowski . . . . . . 156
Skenidioides sp. (i) . . . . . . 156
Skenidioides sp. (2) ....... 156
Superfamily Enteletacea Waagen . . . . . 157
Family Paurorthidae Opik . . . . . . 157
Paurorthis(?) sp. ...... . 157
Family Dalmanellidae Schuchert . . . . . 158
Dalmanella(>} sp. ....... 158
Onniella(>} sp. ........ 158
Family Harknessellidae Bancroft . . . . . 159
Harknessella(?) sp. ....... 159
Horderleyella(l] sp. ....... 159
GEOL. 16, 4. 15
I28 LOWER PALAEOZOIC BRACHIOPOD
Page
Family Linoporellidae Schuchert & Cooper . . . 159
Salopia salteri gracilis Williams . . . . . 159
Family Angusticardiniidae Schuchert & Cooper . . . 160
Rhynchorthis rotundus gen. et sp. nov. .... 160
Superfamily Clitambonitacea Winchell & Schuchert . . 161
Family Polytoechiidae Opik . . . . . . 161
Tritoechia sp. ........ 161
Family Clitambonitidae Winchell & Schuchert . . . 162
Clitambonites(?) sp. . . . . . . . 162
Ilmarinia sp. . . . . . * . 162
Apomatella(l} sp. . . . . . . . 163
Superfamily Gonambonitacea Schuchert & Cooper . . . 163
Family Gonambonitidae Schuchert & Cooper . . . 163
Antigonambonites pyramidalis sp. nov. . . . . 163
Estlandia(l] sp. ........ 164
Family Kullervoidae Opik . . . . . . 165
Kullervo aff. panderi (Opik) . . . . . . 165
Suborder Clitambonitidina Opik . . . . . . 165
Superfamily and genus unknown . . . . . . 165
Superfamily Plectambonitacea Jones . . . . . 166
Family Plectambonitidae Jones . . . . . 166
Ahtiella quadrata sp. nov. . . . . . . 166
Ahtiella concava sp. nov. . . . . . . 167
Reinversella monensis gen. et sp. nov. .... 169
Family Leptestiidae Opik . . . . . . 170
Palaeostrophomena sp. . . . . . . . 170
Palaeostrophomena(>} sp. . . . . . . 171
Family Leptellinidae Ulrich & Cooper . . . . 171
Leptestiina derfelensis (Jones) . . . . . 171
Bilobia aff. musca (Opik) . . . . . . 171
Family Sowerbyellidae Opik . . . . . . 172
Eoplectodonta lenis Williams . . . . . . 172
Ptychoglyptus sp. . . . . . . . . 173
Sericoidea abdita Williams . . . . . . 173
Superfamily Strophomenacea King . . . . . 174
Family Leptaenidae Hall & Clarke . . . . . 174
Leptaena sp. ........ 174
Dactylogonia sp. . . . . . . . . 175
Kiaeromena(l] sp. . . . . . . . 175
Superfamily Porambonitacea Davidson . . . . 176
Family Huenellidae Schuchert & Cooper . . . . 176
Rectotrophia globularis gen. et sp. nov. .... 176
Family Porambonitidae Davidson . . . . . 177
Porambonites (s.s.) sp. . . . . . . . 177
Family Camerellidae Hall & Clarke . . . . . 178
Camerella sp. . . . . . . . . 178
Superfamily Pentameracea M'Coy . . . . . 178
Family Parallelelasmatidae . . . . . . 178
Metacameralla cf. balcletchiensis (Davidson) . . . 178
Order uncertain . . . . . . . . . 179
V. SYSTEMATIC DESCRIPTION OF THE TRILOBITA . . . . 179
Family Asaphidae Burmeister . . . . . 179
Ogygiocaris selwynii (Salter) . . . . . . 179
AND TRILOBITES OF ANGLESEY 129
Family Thysanopeltidae Hawle & Corda . . . . 180
Protobronteus greenlyi sp. nov. ..... 180
Family Illaenidae Hawle & Corda . . . . . 181
Illaenus sp. ........ 181
Stenopareia cf. linnarssoni (Holm) . . . . . 182
Family Harpidae Hawle & Corda . . . . . 183
Selenoharpes(?) sp. ....... 183
Family Trinucleidae Hawle & Corda . . . . . 184
Bergamia(>} sp. ........ 184
Family Raphiophoridae Angelin . . . . . 185
Ampyx sp. (i) . . . . . . . 185
Ampyx sp. (2) . . . . . . . 186
Family Cheiruridae Salter . . . . . . 187
Ceraurinella sp. . . . . . . . . 187
Sphaerexochus sp. ....... 189
Family Pliomeridae Raymond ...... 190
Pliomerops sp. ........ 190
Placoparia sp. ........ 191
Family Calymenidae Burmeister . . . . . 192
Calymenid ......... 192
Family Homalonotidae Chapman ..... 193
Neseuretus monensis (Shirley) . . . . . 193
Family Lichidae Hawle & Corda . . . . . 194
Amphilichas sp. (i) ....... 194
Amphilichas sp. (2) . . . . . . . 195
Family uncertain . . . . . . . . 195
Monella perplex a gen. et sp. nov. . . . . . 196
VI. REFERENCES .......... 197
SYNOPSIS
Arenig sandstones, grits and conglomerates rest unconformably on pre-Cambrian rocks
and contain a shelly fauna with Baltic affinities, predominantly of brachiopods and trilobites.
New brachiopods include Ahtiella quadrata sp. nov., Hesperonomiella carmelensis sp. nov.,
Monorthis typis gen. et sp. nov., Panderina lamellosa sp. nov., Rectotrophia globularis gen. et
sp. nov., Reinversella monensis gen. et sp. nov., Rhynchorthis rotundus gen. et sp. nov. and
Pleurorthis costatus sp. nov. A new trilobite, Monella perplexa gen. et sp. nov. is also present.
Higher Arenig and Llanvirn shales, grits, conglomerates, shaley breccias and ironstones
contain mixed graptolitic and shelly faunas, including one new brachipood, Ahtiella concava.
Lower Caradoc rocks resting unconformably on older Ordovician or pre-Cambrian rocks
comprise conglomerates and breccias with shelly faunas, and ironstones and graptolitic shales.
A brachiopod-graptolite fauna from Llanbabo and Caregonen can be correlated with the Derfel
Limestone fauna of the Arenig district. Limestone blocks in a breccia of the same age yielded
a brachiopod-trilobite fauna, including Protobronteus greenlyi sp. nov.
Graptolitic shales of Llandovery age at Parys Mountain rest on an acid volcanic group of
Caradoc (?) age.
I. INTRODUCTION AND ACKNOWLEDGMENTS
ALTHOUGH Anglesey attracted the attention of several workers in the nineteenth
century, our knowledge of the Ordovician stratigraphy is due mainly to the Geo-
logical Survey Memoir of Greenly (1919), in which use was made of the standard
graptolitic zoning developed by Lapworth, Elles and Wood to date the rocks. The
i3o LOWER PALAEOZOIC BRACHIOPODS
shelly faunas are under-represented in his collections; in particular the important
Caradoc fauna from Llanbabo is not represented at all, though a large graptolite
fauna is listed from the same locality (Greenly 1919 : 455).
The Ordovician fossils have not been the subject of any intensive study since
Greenly 's time, or indeed before it. Few species or genera have been erected from
among them, and identification has been made in most cases by geologists who
were not working on the island. Since the publication of Greenly 's memoir two
papers have contained accounts of some of the fossils from his collection.
Shirley (1936) in his account of the British Calymenidae referred the calymenids
collected by Greenly from the basal beds of the Principal Area to the new species
Synhomalonotus monensis (now Neseuretus monensis}, and Whittard (1956 : 17)
commented on a specimen of Ampyx from the collection. The writer has already
described a new species of gastropod, Mather ella(?) acuticostata, from the Arenig
Treiorwerth Formation (1963).
I wish to thank Professor A. Williams for his guidance throughout this work,
and for his critical reading of the text. The following have commented on specific
aspects of the palaeontology: the late Dr. L. R. Cox, Professor C. Poulsen, Professor
G. Regnell, Dr. I. Strachan, Mr. R. P. Tripp, Professor H. B. Whittington and
Professor A. Wood.
Much of the work was carried out during the tenure of post-graduate scholarships
of the Queen's University of Belfast and the Ministry of Education (Northern
Ireland). Further aid was given by grants from the Systematics Association, and
the Sir D. Owen Evans fund of the University College of Wales, Aberystwyth.
I am grateful for the help given to me by many friends, including staff and students
of the University College of Wales, for their aid in collecting specimens, and for
discussions in the field and laboratory.
II. SYNOPSIS OF STRATIGRAPHY
The Ordovician rocks of Anglesey crop out in a number of areas, separated prin-
cipally by upfaulted blocks of the Mona Complex. In general precise lithological
correlations cannot be made between them, although two suites of arenaceous
and rudaceous rocks are widespread, one of Arenig age and the other Caradocian.
(a) Eastern Angelsey
On the Menai Straits basal conglomerates and grits (the Garth Ferry Grits) rest
on the Mona Complex at Garth Ferry, near Beaumaris, and are overlain by shales
with Ptilograptus. The age of the succession is not known with precision, but since
the Didymograptus extensus zone is present on the Caernarvonshire shore of the
straits between the bridges (Greenly 1919 : 431) the Garth Ferry rocks are probably
of approximately the same age.
The area around Llangoed is poorly exposed, but a shelly fauna was collected
from grey shales (the Tandinas Shales) at Caregonen. The shales are uncleaved
and very soft, grey in colour, with plentiful mica flakes parallel to the bedding.
The succession is complicated by north-dipping thrusts, though the shales appear
to be dipping at low angles. Greenly found the faunas collected from them per-
AND TRILOBITES OF ANGLESEY
132 LOWER PALAEOZOIC BRACHIOPODS
plexing (1919 : 433), as they appeared to be of widely different horizons. This
was due to Lake's identification of Ampyx nasutus Dalman from the shales, a form
known to him only from the Didymograptus Ufidus zone in South Wales, while
the graptolites found were typical of the Nemagraptus gracilis Zone. The Ampyx
is however, possibly a new species, while the associated brachiopods are conspecific
with those from the Derfel Limestone of the Bala district (Whittington & Williams
1955).
The fauna is: Climacograptus antiquus Lapworth (?), Cl. scharenbergi Lap worth,
Climacograptus sp., Nicolella sp., Platystrophia sp., Leptestiina derfelensis (Jones),
Sericoidea abdita Williams, dalmanellid brachiopod, ogygiid trilobite, Ampyx sp. (2),
Sphaerexochus sp., Amphilichas sp. (2), lamellibranch, Echinosphaerites sp.
(b) The Berw Fault Complex
Ordovician rocks (the Berw Group) incorporated in the Berw Fault complex,
crop out at intervals from Pentraeth, at the head of Red Wharf Bay, to Tai Hirion,
south-west of Holland Arms, a lower arenaceous division being succeeded by blue
shales.
Glanmorfa Shales Blue shales ?
Berw Group
Dryll Formation Greywackes with
interbedded shales 300 ft.
Berw-Uchaf Grits Quartz grits and
sandstones 60-100 ft.
North-east of Holland Arms the basal rocks are poorly exposed, but at Bwlch
Gwyn a small exposure of sandstone and shale appears to rest on a pre-Ordovician
felsite (Greenly 1919 : 435), though the junction is probably faulted. The sand-
stone has yielded: Lenorthis proava (Salter), Skenidioides sp., Rhynchorthis rotundus
gen. et sp. nov., Estlandia (?) sp.
The same horizon is exposed in Rhyd-yr-arian ravine, where the stream is crossed
by the road; the following list is from the collections of Greenly and the writer:
Didymograptus hirundo Salter, Lenorthis proava (Salter), Pleurorthis(?) sp., Rhynch-
orthis rotundus gen. et sp. nov., Monorthis(?} sp., Reinversella monensis gen. et
sp. nov., Rectotrophia(?) sp., Antigonambonites(?) sp., polyzoan, crinoid ossicles.
(c) The Llangwyllog Area
The faulted outlier around Llangwyllog is also poorly exposed; though no shelly
fossils have been found the succession commences with an arenaceous division
which is at youngest Llanvirn (Greenly 1919 : 437). Higher shales are Caradoc in
age, and an ironstone is present (the Ty'n-yr-onen Ironstone).
(d) The Principal Area
In the Principal Area the succession is more complete than elsewhere. The
basal arenaceous beds of conglomerate, grit and current-bedded sandstone (the
AND TRILOBITES OF ANGLESEY
133
i34 LOWER PALAEOZOIC BRACHIOPODS
Carmel Formation, the Foel Formation) crop out mainly along the south-east
boundary lying unconformably on the Mona Complex. The Carmel Formation is
exposed from Rhosneigr to within a mile of Llanerchymedd, and comprises a lower
fossiliferous division of sandstones and conglomerates, and an upper sparsely fossili-
ferous division with current bedding. The chief fossiliferous localities are:
(i) by the roadside one-eighth of a mile north-west of Ty-hen (Greenly 1919 :
442). Lenorthis proava (Salter), Hesperonomiella carmelensis sp. nov.,
Neseuretus monensis (Shirley), Ogygiocaris selwynii (Salter), Monella
perplexa gen. et sp. nov.
(ii) in the scarp above Prys-owain-bach cottage, Carmel. L. proava, H. car-
melensis, M. perplexa.
(iii) small quarry pit 100 yds. north-west of Chaen-bach. Ogygiocaris sp.,
N. monensis.
The type material of Monella perplexa comes from an old quarry, now filled in,
400 yds. north of Bryn Gollen Uchaf, half a mile west of Llanerchymedd.
The Foel Formation is at least a partial lateral equivalent of the Carmel Forma-
tion, and only occurs east of Llanerchymedd. It consists of conglomerates succeeded
by flaggy sandstones with shale partings, but has so far proved unfossiliferous.
Above the basal rocks are five variable rudaceous and arenaceous formations
ranging in age from the D. extensus zone to the D. bifidus zone; they pass laterally
and vertically into poorly exposed shales which contain faunas from the D. mur-
chisoni zone.
The Treiorwerth Formation is a thick series of sandstones, grits and conglomerates
derived from Mona Complex schists and jaspers, exposed between Rhosneigr and
Treiorwerth, and resting on the Carmel Formation. South-east of Ffynnon-y-mab,
Trefor, the lowest horizons consist of grey-green siltstones with coarse micaceous
shale partings, which pass up through 350 ft. of siltstones and sandstones to coarse
grits and conglomerates which are typical of the formation. Three hundred yards
south-east of Ffynnon-y-mab (Greenly 1919 : 442) graptolite fragments in the
sandstones were identified by Elles as ITetragraptus headi (Hall). Sandstones in
the same outcrop have a rich fauna, occurring as water-sorted lenticles of disarticu-
lated valves: Lenorthis proava (Salter), Monorthis typis gen. et sp. nov., Pleurorthis
costatus sp. nov., Panderina lamellosa sp. nov., Hesperonomiella(l} sp., Skenidioides
sp. (i), Rhynchorthis rotundus gen. et sp. nov., Reinversella monensis gen. et sp.
nov., Rectotrophia globularis gen. et sp. nov., Porambonites (s.s.) sp., Tritoechia sp.,
Antigonambonites Pyramidalis sp. nov., Mather ella(?) acuticostata Bates, Monella(?)
sp., polyzoan fragments, crinoid ossicles.
The Nantannog Formation is a thick sequence of shales, with a variable rudaceous
content, mainly as scattered pebbles and slabs of phyllite, but sufficiently concen-
trated at certain horizons to produce grits and conglomerates with a shaley matrix.
The lithology persisted from the D. extensus to the D. murchisoni zones, and some
of the lower horizons contain brachiopods of the Nantannog Formation fauna.
A fauna indicative of the D. bifidus zone was found by Greenly at two localities,
AND TRILOBITES OF ANGLESEY 135
on the same strike. From the first, west of the road at the bend 200 yards west of
Fferam-uchaf farm, Llanbabo, Greenly's specimens were re-examined, no more
having been found: D. bifidus (Hall), D. hirundo Salter, Orthambonites (?) sp. (i).
A shelly fauna was found at the second locality, 190 yards south-east of the farm :
D. bifidus (Hall)(?), D. hirundo Salter(P), Lingula sp., Orthambonites (?) sp., Skeni-
dioides sp. (2), Ptychopleurdla sp., Dactylogonia sp., polyzoan fragments, crinoid
ossicles.
Two hundred and fifty yards west-south-west of Fferam uchaf Greenly (1919 :
452) found D. murchisoni (Beck), and his collection also contains: orthid brachiopod,
illaenid pygidium, Bergamia(?) sp., Placoparia sp., Cyclopyge(?) sp.
Laterally and vertically the Nantannog Formation passes into shales or the
Treiorwerth Formation, except at Bod Deiniol, south of Llanbabo, where it is suc-
ceeded by a thick succession of conglomerates, pebbly grits and sandstones, the
Bod Deiniol Formation. The most prominent member is a conglomerate, 80 ft.
thick, which occurs near the base of the formation and forms a scarp south of Bod
Deiniol. The formation probably belongs to the D. bifidus zone, as Greenly records
graptolites from low in the zone at Bodynolwyn-hir (1919 : 444) in beds underlying
the grits, and beds about 100 ft. above the conglomerate member exposed in the
bed of the River Alaw have yielded a pendent Didymograptus. The formation
loses its topographic expression to the south-east towards Ty-bach cottage, and
the grain size becomes finer, although the conglomerate may here be concealed by
drift. Fifty yards north of the cottage the writer succeeded in obtaining a fauna
from massive grits — probably from a horizon above the conglomerate — when a
trench was being excavated in connection with the building of the Alaw reservoir:
Lenorthis sp., Pander ina(?} sp., Paurorthis(?) sp., Apomatella(?) sp., Ahtiella concava
sp. nov.
North of Dulas Bay a succession of alternating sandstones and shales, the Dulas
Formation, with worm burrowing, cone-in-cone concretions, neptunian dykes and
current bedding, is well exposed on the shore and poorly inland. On the shore
it is faulted against shales containing D. bifidus and D. murchisoni zone faunas.
Over much of the Principal Area shales are poorly exposed, and Greenly records
both lower Ordovician and Caradoc faunas from a number of localities; no formal
stratigraphic name is however proposed for them. One new locality, 100 yards
north of Gwredog-uchaf, Rhodogeidio, has a graptolite-trilobite fauna: Dictyonema
sp., D. bifidus (Hall), D. artus Elles & Wood, D. stabilis Elles & Wood, Climaco-
graptus cf. scharenbergi Lapworth, Climacograptus sp., Glossograptus hincksii fim-
briatus (Hopkinson), Bergamia(!} sp.
At Parys Mountain a volcanic suite (the Parys Group) rests on shales (the Parys
Shales) of the D. bifidus zone or later: graptolites have been found in tips from shafts
sunk beneath the volcanic rocks at the west end of the mountain (Greenly 1919 :
458). Although Greenly described the shales immediately beneath and to the
north of the igneous rocks as Hartfell in age there is no palaeontological evidence
for this. The igneous suite, described by Greenly as a felsite sill, is a complex of
rhyolites, autobreccias, ignimbrites, tuffs and shales, intensively cleaved, sheared
and silicified (Hawkins 1966 : 13). Above the Parys Group, in the core of the syn-
136 LOWER PALAEOZOIC BRACHIOPODS
cline, is a succession of shales and mudstones of Silurian age whose relation to the
older rocks is unknown.
Llandeilo fossils (Greenly 1919 : 465) have been found associated with an iron-
stone at Bonw, and also in a borehole at Llangoed (Greenly 1919 : 432). The extent
and thickness of Llandeilo rocks is, however, unknown.
Caradoc rocks are well exposed in the north-west of the Principal Area, where
a variable group of basal rudaceous rocks overlies the Mona Complex. On Mynydd-
y-garn and at Forth Padrig, north of Mynachdy, on both sides of the Carmel Head
thrust a thick series of breccias, overlain by shales and alternating breccia beds
(the Garn Formation), rests on several horizons in the Complex. The breccia
contains slabs of schists and phyllites up to several feet long, and also rounded
blocks of shelly limestone; at Porth Padrig, Greenly records a graptolite fauna
from the N. gracilis zone in the shales, and the blocks have yielded: Cyrtonotella
sp. (2), Palaeostrophomena(?) sp., Ptychoglyptus sp., Kiaeromena(l) sp., Camerella
sp., Metacamerella cf. balcletchiensis (Davidson), Protobronteus greenlyi sp. nov.,
Illaenus sp., Stenopareia sp., Selenoharpes(?) sp., Pliomerops sp.
On Pen-bryn-yr-eglwys, and on the coast to the south, the Mona Complex is
overlain by a sandy and gritty formation, the Crewyn Formation, which varies in
thickness between 60-150 ft. About 2 ft. above the unconformity, 300 yds. east
of Trwyn y Crewyn poorly-preserved shells were found: Orthambonites sp., Plaesi-
omys sp., Platystrophia(?) sp., lamellibranch, crinoid ossicles.
West of Mynachdy, around an old barn called Ysgubor-gader, is a complicated
region of folded and faulted shales, grits and pre-Cambrian rocks. Two small
exposures of grit, apparently resting on the pre-Cambrian, are poorly exposed
225 yds. south-west and 400 yds. west-south-west of the barn, and contain Plaesi-
omys cf. robusta (Bancroft), Orthambonites (?) sp. Dalmanella (s.l.) sp. and a cystid
plate.
In the Llanbabo region Caradoc rocks either rest on or are faulted against gritty
beds of the D. murchisoni zone, but the contact is not exposed (Greenly 1919 :
451-456). The most complete section is seen at Fferam-uchaf where the rocks
strike east- west through the farmyard:
f Llanbabo Church Grits Pebbly grits alternat-
I ing with shales 20 ft. +
Llanbabo Formation ^ Fferam Shales Dark Blue shales 60 ft.
Fferam Ironstone Ironstone and ferri-
I ferous grit 20-40 ft.
The ironstone and succeeding shales are also exposed in an old quarry south of
Llanbabo (Greenly 1919 : 543), and graptolites of the N. gracilis zone were obtained
from the shales in both areas by Greenly and his collectors.
The Llanbabo Church Grits are best exposed in the old quarry 100 yds. south-
west of the church, where 20 ft. of strata are exposed, pebbly graded grit beds up
to 2 ft. thick alternating with silty blue-grey shales. The latter contain a graptolite
fauna, regarded by Elles (in Greenly 1919 : 455) as being high in the N. gracilis
zone, above the Fferam Shales. The grits contain a shelly fauna, mainly of dis-
AND TRILOBITES OF ANGLESEY 137
articulated brachiopod valves, which correlates well with the Tandinas Shales at
Careg-onen, and with the Derfel Limestone of the Arenig area (Whittington &
Williams, 1955): Orthambonites (?) sp. (2), Nicolella humilis Williams, Cyrtonotella
sp. (i), Dolerorthis cf. tenuicostata W'illiams, Platystrophia precedens major Williams,
Ptychopleurella sp. (2), Plaesiomys (Dinorthis) sp., Salopia salteri gracilis Williams,
Onniella(?) sp., Horderleyella(!} sp., Kullervo aff. panderi Opik, Clitambonites(l} sp.,
Ilmarinia sp., Palaeostrophomena sp., Eoplectodonta lenis Williams, Leptaena(l} sp.,
Echinosphaerites sp.
The Llanbabo Church Grits are also exposed at Fferam-uchaf, in the north-east
corner of the field immediately east of the farmhouse (Greenly 1919 : 451 and
outcrop labelled 'conglm.' in fig. 207), with a similar fauna: Orthambonites (?)
sp., Platystrophia(l] sp., Ptychopleurella sp. (2), Plaesiomys sp., Dolerorthis (?) sp.,
Salopia(?} sp., Bilobia aff. musca Opik, Leptestiina sp., Eoplectodonta lenis Williams,
Leptaena sp.
Above the basal Caradoc rocks of the N. gracilis zone are shales, poorly exposed
and of uncertain extent. Greenly (1919 : 454-455) records graptolites from the
zones of Cl. wilsoni and Dicranograptus clingani, from shales at Llanbabo which
probably rest on the Llanbabo Church Grits. There is no evidence of the thickness
of these zones, or of their relation one to another, though the close proximity of
the outcrops to the older Caradocian rocks suggests that the zones are not very
thick.
In the Eilian sector no fossils have been found to add to Greenly's collection
(1919 : 466), which contains Glyptograptus teretiusculus (Hisinger) and Placoparia
sp. The section seen on the shore between the Carmel Head Thrust at Porth-y-
corwgl and the gneisses south of Porth-y-gwichiaid contains a number of units,
separated by faults. Between Porth-y-corwgl and Fresh Water Bay are a series
of conglomerates, pebbly grits and shales (the Fresh WTater Bay Group), all apparently
younging south and overturned. Between Ogof Fach and Ogof Fawr are highly
cleaved and sheared grey shales, intruded by acid sills. On the northern side of
Porth-y-gwichiaid are fine siltstones and mudstones, with some worm burrows,
also cleaved and folded; it is not known in which direction they young. On the
south side of the Porth is a series of siltstones, shales, conglomerates and an iron-
stone, partly slumped in some horizons, and disposed in a complex syncline.
(e) The Gynfor Outliers
On the north coast the Ordovician rocks are exposed in a number of faulted and
folded outliers resting on the Mona Complex. Two groups are present, separated
by a disconformity. The earlier (Porth \Ven Group), of Arenig Age, is of two
conglomerate and grit formations, the lower being a purple conglomerate (the
Hell's Mouth Conglomerate), absent from some exposures, and the upper a pale
brown weathering sequence of conglomerates, grits and sandstones containing an
Arenig fauna (the Torllwyn Formation). Brachiopods were obtained from some
of the localities listed by Greenly (1919 : 469-470) :
(i) 10 ft. above the unconformity on the north side of Ogof Gynfor (exposure
138 LOWER PALAEOZOIC BRACHIOPODS
in Greenly op. cit., PI. XXIX): Rhynchorthis rotundus gen. et sp. nov.,
Estlandia(?) sp.
(ii) about 40 ft. above the unconformity, 45 yds. north of the last locality,
north of the faulted syncline containing Gynfor Shales in the core:
Lenorthis sp., Hesperonomiella(l] sp., Monorthis sp., Panderina cf. lamel-
losa sp. nov., Pleurorthis sp., Skenidioides sp., Rhynchorthis sp., Tritoechia
sp., Antigonambonites sp., Inversella (Reinversellal] sp., Ahtiella quadrata
sp. nov., crinoid ossicles, polyzoan fragments.
(iii) Thirty to forty ft. above the unconformity, on the north side of the ridge of
Mynydd-pant-y-gaseg, 85 ft. east of the summit: Orthambonites(l] sp.,
Ahtiella(?) sp. (poorly preserved).
(iv) in the cutting of the Graig Wen tramway, 70 yds. below the winding house,
collected from loose material: Lenorthis cf. proava (Salter), Panderina(?)
sp., Rhynchorthis^} sp., Antigonambonites (?) sp.
The specimens of Lenorthis examined include a number from the Geological
Survey collection ^1470-1502).
The upper group (Llanbadrig Group) is Caradoc in age, with an ascending se-
quence of cherty shales (Gynfor Shales), an ironstone (Penterfyn Ironstone) and
shales and ferriferous grits (Forth Pridd Formation). Faunas of graptolites from
the lower and upper formations (Greenly 1919 : 470-471) come from the N. gracilis
zone, and hence (it is unlikely that the Arenig fossils are derived) there must be a
plane of disconformity within the Torllwyn Formation or at its top. Erosion
surfaces are present within it, and the contact with the shales above is also abrupt,
with the shales resting on a slightly irregular surface of coarse conglomerate.
The Silurian shales of Parys Mountain lie above the volcanic Parys Group but
the nature of the contact between them is unknown. Greenly (1919 : 481-482)
lists graptolite faunas from all the Llandovery zones. There is no palaeontological
evidence for Silurian rocks at Rhos-mynach (Greenly 1919 : 482-483), and the
shales there are intercalated between rhyolites which are probably equivalent to
the Parys Group.
(f) Faunal Lists
Explanation of symbols: ex. = Didymograptus extensus Zone; hi. = D. hirundo Zone; bi. =
D. bifidus Zone; mu. = D. murchisoni Zone; te. = Glyptograptus teretiusculus Zone; gr. =
Nemagraptus gracilis Zone.
BRACHIOPODA
ex. hi. bi. mu. te. gr.
Ahtiella concava sp. nov. ... X
Ahtiella quadrata sp. nov. ... X
Antigonambonites pyramidalis sp. nov. . x
Apomatella(>) sp. .
Bilobia aff. musca (Opik)
Camerella sp. ..... X ?
Clitambonites(l) sp. .
Cyrtonotella sp. (i)
AND TRILOBITES OF ANGLESEY I39
ex. hi. bi. mu. te. gr.
Cyrtonotella sp. (2) X ?
Dactylogonia sp. .
Dalmanella(?) sp. X
Dolerorthis cf. temncostata Williams
Eoplectodonta lenis Williams .
Estlandia(l) sp. .
Harknessella(?) sp. X
Hesperonomiella carmelensis sp. nov. . X ?
Horderleyella(l] sp. X
Ilmarinia sp. ..... X
Kiaeromena(t) sp. .... X ?
Kullervo aff . panderi (Opik) .
Lenorthis proava (Salter)
Lenorthis sp.
Leptaena sp. ..... X
Leptestiina derfelensis (Jones) . . X
Metacamerella cf . balcletchiensis (Davidson) X ?
Manor this typis gen. et sp. nov. . . X
Nicolella humilis Williams ... X
Onniella(l) sp. .....
Orthambonites(t) sp. (i)
Orthambonites(?) sp. (2) ...
Palaeostrophomena sp. .
Palaeostrophomena(?) sp.
Panderina lamellosa sp. nov. .
Paurorthis(>} sp. .
Plaesiomys sp. ..... X
Plaesiomys cf . robusta (Bancroft) . . X
Plaesiomys (Dinorthis) sp. ... — X
Platystrophia precedens major Williams . X
Plectorthis(?) sp. .
Pleurorthis costatus sp. nov. .
Porambonites (s.s.) sp. .
Ptychoglyptus sp. ..... X ?
Ptychopleurella sp. (i) .
Ptychopleurella sp. (2) .
Rectotrophia globularis gen. et sp. nov.
Reinversella monensis gen. et sp. nov.
Rhynchorthis rotundus gen. et sp. nov.
Salopia salteri gracilis Williams
Sericoidea abdita Williams
Skenidioides sp. (i) . . . X
Skenidioides sp. (2) .... X
Tritoechia sp. ..... X
TRILOBITA
Amphilichas sp. (i) X ?
Amphilichas sp. (2) ....
Ampyx sp. (i) .....
Ampyx sp. (2) .....
Bergamia(l] sp. .....
Calymenid ......
140
LOWER PALAEOZOIC BRACHIOPODS
Ceraurinella sp.
Illaenus sp.
Monella perplexa gen. et sp. nov.
Neseuretus monensis (Shirley)
Ogygiocaris selwynii (Salter) .
Placoparia sp.
Pliomerops sp. .
Protobronfsus greenlyi sp. nov.
Selenoharpes(l] sp.
Sphaerexochus sp.
Stenopareia sp. .
hi.
bi.
tc.
x? — —
x?
x?
X?
X?
X?
X?
— X
— X?
III. FAUNAL AFFINITIES AND CORRELATIONS
The basal rocks of the Principal Area, the Carmel Formation, have a fauna
characterized by few species, but a large number of individuals, especially Lenorthis
proava (Salter), which occurs in vast numbers as disarticulated valves. Similar
species are found elsewhere in Wales at this horizon, at Arenig in the Henllan Ash,
and at St. David's and the Carmarthen- Whitland region. In the latter regions
they are described as Orthis carausii Salter, and are associated with Lenorthis alata
(Salter) . Ogygiocaris selwynii (Salter) and Neseuretus monensis (Shirley) , which are
found sporadically, belong to genera which are widespread throughout Wales at
this time. Monella perplexa gen. et sp. nov. is at present cryptogenic, but may be
a survivor of the Cambrian Corynexochida.
Hesperonomiella carmelensis sp. nov. belongs to a genus described by Ulrich &
Cooper (1938) from the upper Canadian (approximately upper Llanvirn) of much
of North America. The genus is described as having chilidial plates, but in some
cases they are very rudimentarily developed, and in this species are not developed
at all. It is possible that later species of Hesperonomiella and its ally Hesperonomia
have their origin in forms comparable with this species.
Near the base of the overlying Treiorwerth Formation, and at the base of the
system along the Berw Fault is a rich shelly fauna, consisting almost wholly of
brachiopods. Three stocks, Lenorthis proava, Hesperonomiella carmelensis, and
Monella(?) sp. persist from the Carmel Formation, but are joined by a variety of
forms, some new, some with American affinities, and some very similar to contem-
porary Baltic faunas. Rhynchorthis rotundus gen. et sp. nov., Porambonites sp.
and Antigonambonites pyramidalis sp. nov. are closely related to contemporary
Baltic stocks (Alichova 1953, Table i). Porambonites and Antigonambonites appear
similar in morphological grade to the earliest Russian species (of Bj/? in Estonia,
O1v1 on the Russian platform) and one can correlate the Anglesey fauna with con-
fidence with this horizon. Rhynchorthis is similar to Angusticardinia, also from this
level, but appears to be more primitive in its features. Panderina lamellosa is
more advanced than contemporary Russian species, again from this horizon.
Reinversella monensis gen. et sp. nov. is closely related to Inversella Opik from
Estonia and Norway, a later genus from the upper Arenig (Bm and later) (Opik
I933 : 23)- Ahtiella quadraia sp. nov., is a member of a genus which is also found
AND TRILOBITES OF ANGLESEY 141
later in the Baltic region (B^-C^. It is thus probable that the two faunas were
closely linked at this time with migration possible in either direction.
The stocks with American affinities, Pleurorthis costatus sp. nov. and Tritoechia
sp., differ markedly from those just described. In America Pleurorthis is known
from the much later Mystic conglomerate of Quebec and the Table Head Series of
Newfoundland (both upper Llanvirn), with rather different species (Cooper 1956 :
330-333). Tritoechia ranges throughout the Arenig equivalents in North America
(much of the Canadian of Twenhofel et al., 1954, chart 2).
Monorthis typis gen. et sp. nov. is of uncertain affinities, and makes its only known
appearance in this fauna. Skenidioides can probably best be regarded as indigenous,
as it occurs in the Mytton Flags of Shropshire and at Tourmakeady, Co. Mayo
(Professor A. Williams, personal communication), and is also present in the Whitland
region. Rectotrophia globularis gen. et sp. nov. has affinities with both American
and Bohemian forms. Mather ella, a sinistral gastropod, belongs to a small but
widespread group of shells, with both American and Bohemian members.
Llanvirn shelly faunas are sparse, as the sediments are predominantly shaley.
Orthambonites(?) sp. (i) may be regarded as indigenous, being closely related to
Lenorthis, as may Skenidioides sp. (2) descended from the Arenig species. Ahtiella
concava sp. nov. either is descended from the Arenig species, or is a later migrant
from the Baltic region. Ptychopleurella sp. (i) is an atypical member of the genus,
possibly earlier than any of the American species. Trinucleids make their appear-
ance in Anglesey at this time, but are indigenous south British elements which
have been recorded widely within Wales (Whittard 1955-64; Whittington 1966),
and may well have reached Anglesey earlier than this time.
The dominant shelly fauna taken from rocks belonging to the Nemagraptus
gracilis Zone is closely comparable with that found at Derfel, near Arenig (the
Derfel Limestone fauna of Whittington & Williams 1955), which has been divided
into a native association of elements known in Wales from older rocks, together
with stocks which migrated from the east Baltic, Russia, Bohemia and the North
Atlantic Province. As developed in Anglesey the fauna has similar elements.
Native stocks include Orthambonites (?) sp. (2), Ptychopleurella sp. (2), Dinorthis
sp., Eoplectodonta lenis Williams, Sericoidea abdita Williams, Salopia salteri gracilis
Williams, Onniella(?) sp., Horderleyella sp., Amphilichas sp. (2), Ampyx sp. (2),
and trinucleids. Elements regarded by Whittington & Williams as exotic include
Nicolella humilis Williams, Cyrtonotella sp., Dolerorthis cf. tenuicostata Williams,
Platystrophia precedens major W'illiams, Palaeostrophomena sp., Leptaena sp., Leptes-
tiina derfelensis (Jones) and Kullervo aff. panderi Opik. Other stocks occurring
in Anglesey, but not so far found at Derfel, provide further evidence of the Baltic
affinities of the fauna. Bilobia aff. musca Opik has strong affinities with Opik's
species, from this horizon in the east Baltic. Ilmarinia sp. and Clitambonites(l]
sp. also belong to Baltic genera, though Ilmarinia occurs at a higher horizon in
the east. In the light of the affinities of the Arenig faunas discussed above, the
Derfel Limestone fauna is best regarded, not as an invasion of the region by an
entirely new fauna during the N. gracilis transgression, but as the continuation of
an association which existed in the lower Ordovician.
142 LOWER PALAEOZOIC BRACHIOPODS
The fauna of the limestone blocks in the Garn Breccia at Forth Padrig is not
younger than the N. gracilis Zone, and may be older. The trilobites of the lime-
stone are similar to those of the Derfel Limestone, Ceraurinella, Amphilichas and
Illaenus being common to both. Other trilobites in the fauna are Selenoharpes(?)
sp., a calymenid, Piomerops sp. and Protobronteus greenlyi sp. nov. All these may
be traced to the north Atlantic province, to which Whittington attributes Cerauri-
nella(?}, Illaenus (s.l.) and Harpes (s.l.) from the Derfel Limestone. The brachiopods
of the fauna are more ambiguous. Palaeostrophomena(l] sp., Cyrtonotella sp., and
Kiaeromena(t} sp. have Baltic affinities, and the genera occur in the Derfel Lime-
stone. Ptychoglyptus is known from slightly higher horizons in Norway (4b or
the Climacograptus peltifer zone; Spjeldnaes 1957 : 61), and from the Girvan area
in Scotland (Williams 1962 : 193). Camerella and Metacamerella are both found
in Scotland and America. Thus these latter three brachiopod genera, together
with the trilobites, may indicate an intermingling of the Baltic and Scoto-Appala-
chian faunas, at least in the limestone facies, if not in the grits at Llanbabo or in
the Careg-onen and Derfel sediments. It appears likely, from lithological evidence,
that the source area of limestone deposition lay to the north of Anglesey, but prob-
ably still on the upfaulted Irish Sea Landmass.
The specimens examined either come from Greenly's collection or were collected
by the author. Those with numbers prefixed by 'BB' (brachiopods) or Tn' (trilo-
bites) have been donated to the British Museum (Natural History). Greenly's
collection is now in the possession of the Geological Survey, and the specimen
numbers bear the prefix 'Af.
IV. SYSTEMATIC DESCRIPTION OF THE BRACHIOPODA
Order ORTHIDA Schuchert & Cooper 1932
Suborder ORTHIDINA Schuchert & Cooper 1932
Superfamily ORTHACEA Woodward 1852
Family HESPERONOMIIDAE Ulrich & Cooper 1936
Genus HESPERONOMIELLA Ulrich & Cooper 1936
Hesperonomiella carmelensis sp. nov.
(PI. i, figs. 1-6)
1919 Rafinesquina cf. llandeiloensis (Davidson); Matley in Greenly : 142.
DIAGNOSIS. Semicircular to subquadrate Hesperonomiella about three-quarters
as long as wide, hinge line equal to the greatest width, cardinal angles about 80-85°;
valves subequally and gently convex, lateral and anterior commissures plane;
pedicle valve slightly carinate with convex lateral flanks, interarea wide, plane,
apsacline, delthyrium open, width at teeth one-quarter the width of the valve;
brachial valve with shallow rounded sulcus dying out anteriorly, interarea wide,
shorter than the ventral one, anacline, notothyrium wide and open; neither umbo
incurved; ornament finely and unequally multicostellate, costellae flat-topped with
AND TRILOBITES OF ANGLESEY 143
narrow interspaces, numbering thirty per 5 mm. at 5 mm. from the umbo, arising
by bifurcation, every fifth or sixth costella more prominent; teeth triangular, dental
lamellae widely divergent forwards and slightly divergent to the floor of the valve,
short but not receding, continued as low ridges around the muscle scars; muscle
scars triangular in outline and relatively confined to the delthyrium, in length
one-quarter that of the valve, adductor and diductor scars expanding forwards
and equal in length; median trunks of the vascula media slightly impressed, con-
verging forwards from the ends of the diductor scars to come in contact at half the
length of the valve and then diverging again; cardinal process a simple lenticular
septum with low lateral ridges parallel to its posterior half; brachiophores diverging
at 80°, short and triangular in cross section, ends bevelled, largely adpressed to the
valve surface; muscle scars and mantle canals not seen; subperipheral rim present.
TYPE SPECIMENS (measurements in mm.)
Length Width
HOLOTYPE. Internal mould of brachial valve
(66.30529) 17-6 24-4
PARATYPES. Internal mould of pedicle valve
(66.30530) 19-6
Internal mould of pedicle valve
(66.30531) 19-2 26-9
Internal and external moulds of pedicle
valve (66.30532a-b) ....
External mould of brachial valve
(66.30533) 19-3
HORIZON AND LOCALITY. Carmel Formation, sandstone 50 yds. north-east of
Prys-o wain-bach, Carmel. N.G.R. 38878282.
DISCUSSION. Although the family Hesperonomiidae as erected by Ulrich &
Cooper (1938 : 114) was defined as comprising forms with a chilidium, some of the
species described by them have only rudimentary chilidial plates, which may be
interpreted as a thickening of the inner edge of the interareas, and a swelling of the
brachiophores (cf. Ulrich & Cooper 1938, PI. 19, figs. 9, 10, 14, 17). Two genera
were described, Hesperonomia with piano- or concavo-convex valves, and Hes-
peronomiella with gently biconvex valves. The new species therefore belongs in
the latter genus. All the described species have a uniform ornament, whereas the
new species is unequally parvicostellate. Internally the closest species is Hespero-
nomia louisensis Ulrich & Cooper, from the Sarbach formation, Alberta (Ulrich &
Cooper 1938 : 120), which has almost identical ventral musculature and dorsal
cardinalia, but has a concave brachial valve and equally parvicostellate ornament.
The specimens from the type locality are all very uniform in size, and to some
extent distorted. The smallest pedicle valve had a length of 9-1 mm., and in a
sample of eleven pedicle valves the average length was 16-6 mm., with a variance
of 4-42, suggesting that the sample was current drifted with good sorting.
i44 LOWER PALAEOZOIC BRACHIOPODS
Genus MONORTHIS nov.
DIAGNOSIS. Quadrate shells, widest at a long straight hinge line, alate, with
slightly acute cardinal angles; lateral profile flatly biconvex, with very low pyra-
midal pedicle valve and evenly convex brachial valve; pedicle valve with a low
carinate fold with plane flanks, the rest of the surface evenly convex, almost flat;
brachial valve with a deep rounded sulcus, swollen folds on either side of it, and
concave lateral margins; lateral commissure flat, anterior commissure uniplicate;
ventral interarea short and wide, apsacline to almost catacline, delthyrium open,
dorsal interarea shorter, anacline, notothyrium open; surface finely multicostellate.
Ventral interior with receding dental lamellae, teeth and musculature not seen.
Dorsal interior with elevated notothyrial cavity; cardinal process a thin ridge;
brachiophores thin and short, supported by a mass of callus, sockets thin and deep ;
adductor scars not seen but separated by a large median ridge corresponding to
the exterior sulcus.
TYPE SPECIES. Monorthis typis sp. nov. from the Treiorwerth Formation.
DISCUSSION. The simple cardinalia in the brachial valve, together with the
transverse shape and the convexity of valves, form the distinctive features of the
genus. Metorthis Wang is similar in shape, but has a thickened cardinal process
and muscle scars like those of Dinorthis, whereas this genus seems to have the
confined muscle scars of Orthis. The genus is tentatively placed in the Hesperono-
miidae, since it agrees with the diagnosis of that family (Ulrich & Cooper 1938 :
114) except that neither chilidial plates nor a chilidium are present. The structure
interpreted by Ulrich & Cooper as chilidial plates may be no more than the thick-
ening of the inner edge of the interarea where it forms the posterior part of the
brachiophores.
Monorthis typis gen. et sp. nov.
(PI. i, figs. 7-13)
1919 Orthis (Hebertella) vespertilio J. de C. Sowerby; Matley in Greenly : 442.
DIAGNOSIS. Quadrate biconvex Monorthis, widest at a long straight hinge-line,
alate, with slightly acute cardinal angles; lateral profile flatly biconvex, with very
low pyramidal pedicle valve and an evenly convex brachial valve; pedicle valve
with a low carinate fold with plane flanks, the rest of the surface evenly convex,
almost flat, interarea short and wide, apsacline to almost catacline, delthyrium
open; brachial valve with a deep rounded sulcus, swollen folds flanking it, and
concave lateral margins, interarea shorter than the ventral one, anacline, noto-
thyrium open; surface of both valves finely multicostellate, costellae numbering
four per mm. at the shell margins but everywhere poorly preserved; ventral interior
with receding dental lamellae, teeth not seen; musculature not seen but probably
confined ; low ridges marking the sides of the fold are aligned with the dental lamellae ;
dorsal interior with small elevated notothyrial platform; cardinal process a thin
ridge; brachiophores short and thin, supported by a mass of callus cementing them
AND TRILOBITES OF ANGLESEY 145
to the sides of the notothyrial cavity; sockets thin and deep; adductor scars prob-
ably small, and separated by a large median elevation corresponding to the exterior
sulcus.
Length Width
TYPE SPECIMENS (measurements in mm.)
HOLOTYPE. Internal mould of brachial valve
(BB. 30534) 7-1
PARATYPES. Internal and external mould of brachial
valve (BB.30535a-b) . . . 6-9
Internal and external moulds of pedicle
valve (BB . 30536a-b) . . . 7-1 n-o
TYPE HORIZON AND LOCALITY. Treiorwerth Formation, sandstones 300 yds.
south-east of Ffynnon-y-mab, Trefor. N.G.R. 36247950.
DISCUSSION. The new species is generically distinct from other known ortha-
ceans, and can be distinguished by features referred to in the generic description
from various hesperonomiids with which it is most closely related. The poor
preservation of the valves makes it impossible to carry out any analysis of the
ribbing or of the various dimensions, except to remark that the average percentage
length of five brachial valves relative to width was 62-6 (range 55 '3-73*4).
Family ORTHIDAE Woodward 1852
Subfamily ORTHINAE
Genus CYRTONOTELLA Schuchert & Cooper 1931
Cyrtonotella sp. (i)
(PI. 2, figs. 9, 10, 13)
FIGURED SPECIMEN (measurements in mm.)
Length Width
Internal and external mould of brachial valve
(BB.3o52ia-b) ....
HORIZON AND LOCALITY. Llanbabo Formation, Llanbabo Church Grits, Church
Quarry, Llanbabo. N.G.R. 37758672.
DISCUSSION. Two valves have been found, one being very incomplete, the other
a brachial valve in fair condition. It is semi-circular, with a slight sulcus. The
hinge-line is straight, with an anacline interarea and probably an open notothyrium.
The ornament is multicostellate ; the margin has more than forty ribs but the
details of the branching are obscure. Internally the cardinal process is simple
and continuous with a median septum, the brachiophores are orthoid, diverging
at 80°, and the sockets are elongated parallel to the hinge-line. These characters
agree well with those of the brachial valve figured by Williams (in Whittington &
Williams 1955, pi. 38, figs. 14-16), and referred to Cyrtonotella aff. kukersiana
(Wysogorski) .
146 LOWER PALAEOZOIC BRACHIOPODS
Cyrtonotella sp. (2)
(P.. 2, figS. 14-16)
Length Width
FIGURED SPECIMENS (measurements in mm.)
Exterior of incomplete pedicle valve (BB . 30522) . 7-9
Exterior of incomplete brachial valve (66.30523) . 13-5
External mould of incomplete brachial valve
(66.30524) . 8-9
HORIZON AND LOCALITY. Garn Formation, Limestone blocks in breccia beds,
Forth Padrig, Mynachdy. N.G.R. 30539279.
DISCUSSION. The valves have the external features of Cyrtonotella, but the
interareas and the internal features are concealed. The pedicle valve is strongly
convex, and is probably semi-circular in outline with a straight, slightly alate
hinge-line ; the interarea cannot be very long. The brachial valve is gently concave,
with a slight median sulcus in one specimen (66.30524). The ornament of both
valves is slightly fascicostellate, with seven to twelve costellae per 5 mm. antero-
medianly, and the interspaces have closely spaced fine growth lines. The pattern
of the branching of the ribs cannot be made out. Owing to the incompleteness
of the valves it is not possible to compare them closely with any other species.
Genus LENORTHIS Andreeva 1955
Lenorthis proava (Salter)
(PL i, fig. 21 ; PI. 2, figs. 1-8)
1866 Orthis calligramma var. proava Salter: Appendix 335-336, pi. 22, fig. i.
1868 Orthis Carausii (Salter ms.); Davidson : 315, pi. 16, fig. 23.
1869 Orthis Carausii (Salter ms.); Davidson : 229, pi. 33, figs 1-7.
1869 Orthis calligramma var. proava Salter; Davidson : 241, pi. 35, figs. 13-15.
1883 Orthis carausii Salter; Davidson: 182-184, pi- J4- ^g8- 21-26.
1912 Orthis proava Salter; Matley : 78-79.
DIAGNOSIS. Subquadrate biconvex Lenorthis five-sixths as long as wide and
one-third as deep as wide, the pedicle valve being twice as deep as the brachial
valve; widest at the hinge line, with cardinal angles of approximately 90°, anterior
and lateral commissures plane; pedicle valve convex, slightly carinate, interarea
curved, apsacline, one-sixth the length of the valve; brachial valve gently convex
with a shallow rounded median sulcus and concave flanks, interarea anacline,
shorter than the ventral one ; ornament of simple rounded costae with equal rounded
interspaces, numbering sixteen to twenty, with a wave-length of 0-93 mm. at 5 mm.
from the dorsal umbo, the pedicle valve bearing a median costa and the brachial
valve four costae in the sulcus ; costae covered by fine filae, growth lines rarely seen
except at the margins of adult shells; ventral interior with blunt triangular teeth
and small crural fossettes; dental lamellae vertical, receding; muscle scars confined
to the delthyrium but details not seen, width three-twentieths that of the valve,
length length unknown; dorsal interior with thick median septum running half
the length of the valve; adductor scars quadripartite, on either side of the septum,
AND TRILOBITES OF ANGLESEY 147
occupying four-tenths the width of the valve; margins of both valves crenulated.
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal mould of brachial valve (BB. 30512) . 10-5 I5'i
Internal and external moulds of pedicle valve
(BB.305i3a-b) 11-7 15-8
Internal mould of pedicle valve (66.30514) . . distorted
Internal and external moulds of brachial valve
(BB.305i5a-b) . . . . n-o
Internal mould of pedicle valve (Af . 1337) . . 11-4 15*0
HORIZON AND LOCALITIES. Carmel Formation, sandstones, 50 yds. north-east
of Prys-owain-bach cottage, Carmel. N.G.R. 38878283. Specimen Af . 1337 is from
the same horizon, 130 yds. north-west of Ty-hen, Treiorwerth. N.G.R. 35567872.
DISCUSSION. The specimens of L. proava from all the localities in the Carmel
Grits are preserved in a coarse sandstone, so that the finer detail of the ornament
and of the mantle canal patterns is lost. It is seldom possible to count all the
costae, since the finer ribs close to the hinge line are not preserved, and the anterior
border of the ventral muscle scars is not seen. These scars may be triangular in
shape, with the adductors not enclosed by the diductors and equal in length to
them. In ten brachial valves the costae 5 mm. anteromedianly from the umbo
have a mean wavelength of 0-93 mm. (var 0-0141). In the interior of the brachial
valve the anterior and posterior adductor scars are equal in area, the posterior pair
deeply sunk beneath the notothyrial platform. The brachiophores are closely
adpressed to the edges of the platform, and the ends are bevelled.
The majority of the figured specimens come from Prys-owain-bach, as here the
species may be found in greatest abundance, and without much distortion. When
first described by Salter, the locality was given as 'grits among the black shales of
Llanerchymedd, Anglesey' (1866 : 336). No type locality is given for the figured
specimens, which have since been lost. Earlier in the same work (259) the species,
as Orthis calligramma var., is listed as occurring at a locality one mile north-west of
Llanerchymedd, at Treiorwerth, and at Tyn-twr, 4 miles south of Llangefni. The
first of these localities cannot easily be located, and good specimens are not found
in that region; the second locality is that listed above at Ty-hen.
TABLE i
(a) (b)
1 (var. i) 10-36 (5-017) 9-44 (2-600)
w (var. w) 12-12(5-438) 12-70(3-736)
r 0-753 0-787
a (var. a) 1-041 (0-01339) i'J99 (0-01092)
a (var. b) i • 34 (i • 513) i • 38 (i • 0054)
TABLE i. Statistics of length (1) and width (w) of (a) thirty-five pedicle valves and
(b) fifty brachial valves of Lenorthis proava (Salter) from sandstones 50 yds. north-east of
Prys-owain-bach, Carmel,
148 LOWER PALAEOZOIC BRACHIOPODS
Lenorthis sp.
(PI. 2, figS. 11-12)
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal mould of pedicle valve (BB.3o6oia)
Internal mould of brachial valve (BB . 30602) . 11-7 14-6 (est.)
HORIZON AND LOCALITY. Bod Deiniol Formation, grits in temporary excavation
50 yds. north of Ty-bach cottage, Bod Deiniol. N.G.R. 37688528.
DISCUSSION. The species is very similar to Lenorthis proava, and is probably
closely related. The ratio of length to width of the brachial valve is very similar;
in five valves the mean length is 9-56 mm. and width 12-68 mm. There may,
however, be more costae, as at least twenty-four can be counted in some specimens,
and their wavelength 5 mm. from the umbo in the brachial valves is approximately
0-75 mm. compared with 0-95 mm. in L. proava.
Genus ORTHAMBONITES Pander 1830
Orthambonites (?) sp. (i)
(PI. i, figs. 14, 16, 17)
1919 Orthis cf. proava Salter; Matley in Greenly : 452.
FIGURED SPECIMEN (measurements in mm.)
Length Width
Internal and external moulds of brachial valve
(Af. 1398-9) . 6-9
HORIZON AND LOCALITY. Nantannog Formation, gritty shales by well on the
west side of the road, 220 yds. west of Fferam-uchaf. N.G.R. 36188667.
DISCUSSION. The valve has about twenty rounded costae, with late internal
and external bifurcations, and with fine parvicostellae in the interspaces. In
shape the valve is semicircular, with rounded cardinal angles and the greatest
width just anterior to them, gently convex and slightly sulcate. The internal
details are similar to those of Lenorthis proava (Salter). Division of the costae is
described by Cooper (1956) in two species, 0. bifurcatus and 0. divaricatus. The
latter species, with its few late bifurcations, is very similar.
Orthambonites (?) sp. (2)
(PI. i, figs. 15, 18-20)
DESCRIPTION. Small subcircular Orthambonites or Lenorthis with the more con-
vex pedicle valve four-fifths as long as wide and one quarter as deep as long, orna-
mented by about seventeen rounded costae with a wavelength of 07 mm. at 5 mm.
from the ventral umbo.
AND TRILOBITES OF ANGLESEY 149
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal mould of pedicle valve (66.30510) . . 10-7 12-0
Internal and external moulds of pedicle valve
(BB.305na-b) 4-96-3
HORIZON AND LOCALITY. Llanbabo Formation, Llanbabo Church Grits, Church
Quarry, Llanbabo. N.G.R. 37758672.
DISCUSSION. A few pedicle valves of Orthambomtes(?) have been found from
the Llanbabo Grits, together with a few fragmentary brachial valves. The numbers
found are too few to analyse statistically, the mean length and width of three pedicle
valves being 8-7 mm. and 10-1 mm. respectively. The species recalls 0. parvicrassi-
costatus Cooper, from the Caradoc of the Girvan area (Williams 1962 : 98), which
has about nineteen costae on the pedicle valve, angular in cross section. Neither
this species nor the preceding one can be definitely assigned to Orthambonites,
since the course of the vascula media has not been observed.
Genus PLEURORTHIS Cooper 1956
Pleurorthis costatus sp. nov.
(PI. 2, figs. 17-19; PI. 3, figs. 1-4, 6)
DIAGNOSIS. Subequally biconvex, transverse, subquadrate to semicircular
Pleurorthis, length seven-tenths the maximum width, which is at or just anterior to
the hinge-line ; cardinal angles rounded to slightly acute ; lateral commissures almost
straight, anterior commissure uniplicate; pedicle valve initially with a median
fold, reversing to form a sulcus with gently curved flanks at about 3-4 mm. from
the umbo; ventral interarea slightly curved, apsacline, about one-fifth the length
of the valve; brachial valve initially with a slight sulcus, reversing to form a fold
corresponding to the ventral sulcus, interarea wide, anacline, shorter than the ven-
tral one, notothyrium open; ornament on both valves of sharp angular costae,
about ten being primary, increasing by bifurcation and numbering about eight per
5 mm. antero-medianly at 5 mm. from the umbo, growth lines not seen; in ventral
interior teeth blunt, triangular, dental lamellae descending vertically to the floor
of the valve and slightly receding, diverging anteriorly at 70°; muscle scars largely
confined to the delthyrial cavity, elevated on a callosity ending anteriorly in a
blunt forward pointing 'V; adductor track equal in width to one diductor scar,
both sets of scars expanding forwards ; vascula media trunks parallel and submedian ;
in dorsal interior notothyrial platform low, one-sixth the width of the valve ; cardinal
process a simple ridge ; brachiophores blade-like, diverging from each other at more
than 90°, supported only by the notothyrial platform; sockets are pits just below
the hinge-line; adductor scars extend to the midlength of the valve, separated by
a median ridge of the same length, the posterior pair the smaller, wider than long,
anterior pair triangular, coming to a blunt point close to the ridge; costellae im-
pressed on the inner surface of young valves.
i5o LOWER PALAEOZOIC BRACHIOPODS
TYPE SPECIMENS (measurements in mm.)
HOLOTYPE. Internal mould of brachial valve
(BB. 30516)
PARATYPES. Internal and external moulds of pedicle
valve (BB.3o5i7a-b)
Internal mould of pedicle valve
(BB. 30518)
Internal and external moulds of brachial
valve (BB.30555a-b)
Length Width
10-5 19-9
I2-O
7'9
TYPE HORIZON AND LOCALITY. Treiorwerth Formation, sandstones, 300 yds.
south-east of Ffynnon-y-mab, Trefor. N.G.R. 36247950.
DISCUSSION. The new species conforms to the generic diagnosis of Pleurorthis,
but differs markedly from the species described by Cooper (1956 : 329-333). The
ornament is much more coarsely costellate than even the coarsest described by
him, the development of fold and sulcus is much more pronounced, and internally
the described species have no excessive development of secondary calcite in the
larger shells. This last trend in the new species gives rise to a pseudospondylium,
and leads to the obliteration of all internal impressions of the costellae.
I (var. 1)
w (var. w)
r
a (var. a)
b (var. b)
TABLE 2
(a)
8-56(3-433)
12-26 (5-610)
0-867
1-124 (0-00653)
2-639 (0-509I)
(b)
7-55 (2-891)
11-40 (6-181)
0-842
1-462 (0-01152)
0-368 (0-6392)
TABLE 2. Statistics of length (1) and width (w) of (a) forty-eight pedicle valves, and
(b) fifty-four brachial valves of Pleurorthis costatus sp. nov. from sandstones 300 yds.
south-east of Ffynnon-y-mab, Trefor.
Subfamily PRODUCTORTHINAE Schuchert & Cooper 1931
Genus NICOLELLA Reed 1917
Nicolella humilis Williams
(PL 3, ngs. 5, 7-9)
FIGURED SPECIMENS (measurements in mm.)
Internal and external moulds of brachial valve
(BB.3o5i9a-b)
Internal and external moulds of brachial valve
(BB.3052oa-b)
Length Width
10-5 18-4 (est.)
10 -i
AND TRILOBITES OF ANGLESEY 151
HORIZON AND LOCALITY. Llanbabo Formation, Llanbabo Church Grits, Church
Quarry, Llanbabo. N.G.R. 37758672.
DISCUSSION. Specimen 66.30520 has, as far as can be seen, an identical ribbing
pattern to that of N. humilis, with possibly eighteen primary costae, though no
secondary costae are developed, because of the small size of the valve. 66.30519
is also referred to this species; there appear to be only fourteen primary costae,
allowing for state of preservation, and internal and external secondary costae
originate at 5-6 mm from the umbo.
Genus PANDERINA Schuchert & Cooper 1931
Panderina lamellosa sp. nov.
(PL 3, figs. 10-18)
DIAGNOSIS. A species of Panderina with semicircular alate valves, three-quarters
as long as wide, the pedicle valve with the greater convexity, evenly convex medianly
with concave lateral flanks; the brachial valve gently convex with a shallow sulcus,
narrow posteriorly but rapidly widening; anterior commissure slightly uniplicate;
radial ornament of low rounded costellae arising by implantation, crossed by im-
bricate growth lamellae, which become crowded together at the shell margin in
fully grown forms, especially on the brachial valve; ventral interior with stout
dental lamellae descending directly to the floor of the valve, extended as low ridges
bounding an ovate muscle area; teeth blunt, with large and prominent crural fossettes
lying close beneath them and rimmed by accessory teeth ; dorsal interior with large
cardinalia projecting above the hinge line, the width between the brachiophore
tips being four-tenths the width of the valve; brachiophores blade-like, with
massive knob-like ends, diverging at 90° and adpressed to the notothyrial plat-
form; cardinal process a bulbous myophore without shaft, joined to the brachio-
phores at its posterior end; muscle scars extend to the longitudinal midline of the
valve, the anterior pair the larger, not bilobed.
TYPE SPECIMENS (measurements in mm.)
Length "Width
HOLOTYPE. Internal and external moulds of brachial
valve (66 . 30525a-b) . . . . 5-2
PARATYPES. Internal and external moulds of pedicle
valve (66 . 30526a-b) . . . 4-8 6-7
Internal and external moulds of pedicle
valve (88.30527a-b) ... 9-0 (est.)
Internal and external moulds of brachial
valve (66 . 30528a-b) . . . 6-8 9-0 (est.)
TYPE HORIZON AND LOCALITY. Treiorwerth Formation, sandstones 300 yds.
south-east of Ffynnon-y-mab, Trefor. N.G.R. 36247950.
DISCUSSION. The known species of Panderina were all erected by Pander and
Lamansky (Schuchert & Cooper 1932 : 82), and form a homogeneous group of shells
with characteristics 'intermediate between Orthis s.s. and Productorthis . All have
i52 LOWER PALAEOZOIC BRACHIOPODS
piano- or concave-convex shells, short interareas, simple cardinalia, and are im-
bricate anteriorly. The new species has imbricate growth lamellae, but they are
not confined to the front of the shell. The brachial valve is also distinctly convex,
though the specimens are distorted and the degree of convexity cannot be accurately
measured. The cardinalia approach the Productorthis type, and are larger than in
the other described species. It can be seen therefore that the new species has
characters which place it a little further towards Productorthis than the other species
of Panderina.
Family DOLERORTHIDAE Opik 1934
Subfamily DOLERORTHINAE Opik 1934
Genus DOLERORTHIS Schuchert & Cooper 1931
Dolerorthis cf. tenuicostata Williams 1955
(PI. 4) figs. 4, 6-7)
FIGURED SPECIMEN (measurements in mm.)
Length Width
Internal and external moulds of pedicle valve
(BB . 3o54ia-b) . . . . . . n-o
HORIZON AND LOCALITY. Llanbabo Formation, Llanbabo Church Grits, Church
Quarry, Llanbabo. N.G.R. 37758672.
DISCUSSION. One specimen has been found, and shows the interarea and umbonal
regions. Externally the ribs appear similar to those of D. tenuicostata, but since
the specimen is not complete the patterns cannot be compared. Internally the
muscle scars are of the same pattern, though the ridges bounding the diductor
scars make an angle of 90° with each other while in the holotype of the species this
angle is about 60°. The vascula media are typical of the genus. Since the brachial
valve has not been found, and the full ribbing pattern cannot be analysed, the
specific identification is not certain.
Subfamily GLYPTORTHINAE Schuchert & Cooper 1931
Genus PTYCHOPLEURELLA Schuchert & Cooper 1931
Ptychopleurella sp. (i)
(PI. 3, figs. 19-23)
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal and external moulds of pedicle valve
(BB.30537a-b) . . 3 '5
Internal and external moulds of brachial valve
(BB.3o538a-b) 4-5
AND TRILOBITES OF ANGLESEY 153
HORIZON AND LOCALITY. Nantannog Formation, fine sandstones and shales
south-east of Fferam-uchaf farm, Llanbabo. N.G.R. 36518657.
DISCUSSION. The valves have the typical form of Ptychopleurella : the pedicle
valve is sub-pyramidal, with a long, almost catacline interarea, the brachial valve
is convex, with a median sulcus and a shorter, almost orthocline interarea, and
both valves have typical interiors for the genus. The ornament is of simple, angular
costae, fourteen on the brachial valve, with two in the sulcus, originating just
anterior to the umbo. It is crossed by imbricate growth lamellae, crowded together
in the first 5 mm. of growth, subsequently occurring at three per mm.
Only three pedicle valves and two brachial valves have been found, so that no
good estimates of the size and shape parameters of the stock can be gained. The
ratios of length to width as a percentage of the pedicle valve are 56 • 3, 58 • 8 and 79 • 7,
and of the brachial valves 60-0 and 70-0. Without more material it is impossible
to make any good comparisons with described species. In the simple ribs this
species contrasts with Ptychopleurella sp. (2) from Llanbabo, and is similar to other
early species, such as P. oklahomensis Cooper from the McLish formation, Llanvirn
Series (Cooper 1956 : 388).
Ptychopleurella sp. (2)
(PL 4, figs. 1-3, 5)
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal mould of incomplete brachial valve (BB.
Internal and external moulds of incomplete pedicle
valve (BB.3054oa-b) ..... 6-8 8-6(est.)
HORIZON AND LOCALITY. Llanbabo Formation, Llanbabo Church Grits, Church
Quarry, Llanbabo. N.G.R. 37758672.
DISCUSSION. The valves found are small, biconvex and transverse, with a strongly
convex pedicle valve with a median flattening and a strongly apsacline interarea,
and a convex brachial valve with possibly a slight median fold and an almost ortho-
cline interarea. The ornament is of coarse angular costae, increasing by implan-
tation and crossed by close imbricate growth lamellae numbering eight per mm.
at 6 mm. from the ventral umbo. Internally the dental lamellae are receding;
the ventral musculature is well defined and elevated on a pseudospondylium, the
adductor tracks being wide and shorter than the diductor tracks; the cardinalia
are large, the cardinal process being a simple ridge somewhat thickened on its
anterior edge.
The species is similar to the later species of Ptychopleurella, e.g. P. bouchardi
(Davidson) from the middle Silurian, which have ribbing patterns characterized
by late developing secondary costae. The slight median fold of the brachial valve,
if found on other specimens, may prove to be a diagnostic feature, since it is not
found in other species of the genus.
154 LOWER PALAEOZOIC BRACHIOPODS
Family PLAESIOMYIDAE Schuchert 1913
Subfamily PLAESIOMYINAE Schuchert 1913
Genus PLAESIOMYS Hall & Clarke 1892
Plaesiomys cf. robusta (Bancroft)
(PI. 4> figs. 8-12)
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal and external moulds of pedicle valve
(BB.30544a-b) 23-5 32-5
Internal and external moulds of pedicle valve
(BB.30545a-b) . 25-0 26-6 (est.)
Internal and external moulds of brachial valve
(BB.30543a-b) ... .15-0
HORIZON AND LOCALITY. Crewyn Formation, grits in small outcrop 420 yds.
west-south-west of Ysgubor-gader, Mynachdy. N.G.R. 29589214.
DISCUSSION. Both valves have the typical characters of Plaesiomys in shape,
ventral musculature, and cardinalia. The very poorly preserved external moulds
have costellate ribbing. The pedicle adjuster scars are very distinct, the diductor
scars slightly bilobed, and the adductor scars not differentiated. The length of
the two pedicle valves varies from 70-90 per cent, of their width. Strong internal
plications extend inwards from the margin. These features are listed by Bancroft
(1945 : 244-245) as characteristic of P. robusta. He gives little idea of the natural
variation within the species, and unfortunately does not figure a typical pedicle
valve, but only one described by him as abnormal.
Plaesiomys (Dinorthis) sp.
(PL 4, figs. 13-15)
FIGURED SPECIMEN (measurements in mm.)
Length Width
Internal and external moulds of pedicle valve
(BB . 30542a-b) . . . . . . 8-0 10-0
HORIZON AND LOCALITY. Llanbabo Formation, Llanbabo Church Grits, Church
Quarry, Llanbabo. N.G.R. 37758672.
DISCUSSION. The valve is of a subquadrate Dinorthis, convex at the umbo, but
becoming flat towards the commissure, the interarea short and apsacline, with an
open delthyrium, and a simple costate ornament of eighteen costae, becoming
broad and flat-topped towards the anterior. In the interior the muscle scars are
subquadrate and slightly indented medianly, though the individual scars cannot
be separated. The dental lamellae are widely divergent. The shape of the valve,
AN DTRILOBITES OF ANGLESEY 155
and the number of costae suggest a young specimen of D. flabellulum (J. de C.
Sowerby) .
Family PLECTORTHIDAE Schuchert & Le Vene 1929
Subfamily PLEGTORTHINAE Schuchert & Le Vene 1929
Genus PLECTORTHIS Hall & Clarke 1892
Plectorthis (?) sp.
(PI. 4, figs. 16, 19)
1919 Orthis (Dalmanella) testudinarial Dalman; Matley in Greenly : 452.
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal mould of pedicle valve (Af. 1377) . . 6-6 8-0
Internal mould of pedicle valve (Af. 1462) . . 8-5
HORIZON AND LOCALITY. Nantannog Formation, gritty shales 250 yds. west-
south-west of Fferam-uchaf, Llanbabo. N.G.R. 36178655.
DISCUSSION. The valves are convex, suboval in outline with a straight hinge-
line narrower than the maximum width, and a short curved apsacline interarea
and open delthyrium. The ornament is finely costellate. The teeth are not seen,
the dental lamellae are thin and sub-parallel, the muscle scars extend one-third
the length of the valve with the adductor and diductor scars the same length and
with a rectangular end.
Subfamily PLATYSTROPHIINAE Schuchert & Le Vene 1929
Genus PLATYSTROPHIA King 1850
Platystrophia precedens major Williams 1955
(PL 4, figs. 17-18)
FIGURED SPECIMEN (measurements in mm.)
Length Width
Internal and external moulds of pedicle valve
(BB.30546a-b) 13-5
HORIZON AND LOCALITY. Llanbabo Formation, Llanbabo Church Grits, Church
Quarry, Llanbabo. N.G.R. 37758672.
DISCUSSION. Isolated valves referable to Platystrophia have been found at
Careg-onen, Trwyn y Crewyn and Llanbabo. Only at the last locality are the
valves complete enough for a specific identification, and appear to be identical
with specimens from the Derfel Limestone (Whittington & Williams 1955 : 402,
pi. 38, figs. 24-29). The other specimens, in all probabliity from the same horizon,
also belong to the bicostate species group.
156
LOWER PALAEOZOIC BRACHIOPODS
Family SKENIDIIDAE Kozlowski 1929
Genus SKENIDIOIDES Schuchert & Cooper 1931
Skenidioides sp. (i)
(PI. 5, figs. 1-2)
FIGURED SPECIMENS (measurements in mm.)
Length
2-3
Width
Internal mould of pedicle valve (BB . 30547) .
Internal mould of brachial valve (BB . 30548) . 3-2
HORIZON AND LOCALITY. Treiorwerth Formation, sandstones 300 yds. south-
east of Ffynnon-y-mab, Trefor. N.G.R. 36247950.
DISCUSSION. The specimens are preserved as internal and external moulds in
a coarse grit, and are too poorly preserved to identify specifically. In particular
the costae are hardly preserved at all, though they are probably few in number,
between 13 and 16, and simple. The pedicle valve is semicircular, pyramidal,
with a long strongly apsacline interarea and a high-standing shallow spondylium
supported by a short receding median septum. The brachial valve is gently convex
and sulcate, and bears a well developed median septum running the length of the
valve.
TABLE 3
1 mm. (var. 1)
w mm. (var. w)
r
a (var. a)
b (var. b)
2-47 (0-203)
3'53 (0-306)
0-723
1-245 (0-0493)
0-45 (0-3126)
TABLE 3. Statistics of length (1) and width (w) of fifteen pedicle valves of Skenidioides sp. (i)
Skenidioides sp. (2)
(PI. 5, figs. 3-5)
FIGURED SPECIMENS (measurements in mm.)
Internal and external moulds of brachial valve
Length Width
) 2-3
Internal and external moulds of pedicle valve
(BB.3055oa-b) 2-6
HORIZON AND LOCALITY. Nantannog Formation, fine sandstones and shales
190 yds. south-east of Fferam-uchaf, Llanbabo. N.G.R. 36518657.
DISCUSSION. The specimens are typical of the genus, but are very small. The
pedicle valve is sub-pyramidal, with a shallow, largely free spondylium. The
brachial valve has a good septalium, the supporting plates converging on a high
median septum which runs most of the length of the valve. The ornament of both
valves is of simple costae, apparently about fourteen in number.
AND TRILOBITES OF ANGLESEY 157
This species is very similar to Skenidioides sp. (i) from the D. hinmdo zone,
but there seem to be minor differences between the interiors of the two species.
The earlier species has a well developed median septum in the pedicle valve, possibly
with a larger delthyrium. The dorsal sulcus also seems to be better developed in
this species.
Superfamily ENTELETACEA Waagen 1884
Family PAURORTHIDAE Opik 1933
Genus PAURORTHIS Schuchert & Cooper 1931
Paurorthis (?) sp.
(PI. 5, ngs. 6-9)
DESCRIPTION. Pedicle valve subcircular, evenly convex, about one-third as
deep as long and slightly longer than wide ; hingeline slightly less than the maximum
width; interarea curved, apsacline, delthyrium open; ornament fascicostellate but
not well preserved; umbonal cavity deep; muscle scars extending forwards beyond
the umbonal cavity to almost half the length of the valve, elevated anteriorly;
central (adductor?) scars occupying most of the width between the dental lamellae,
flanked by narrow, slightly depressed (diductor?) tracks which extend onto the
sides of the dental lamellae, which extend alongside them as ridges ; teeth apparently
aligned along the dental lamellae, crural fossettes present; vascula media at first
converging from the ends of the diductor scars, then diverging; margin of valve
crenulate.
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal mould of pedicle valve (BB . 3o6o3a) . 9-5 10-2
Internal and external mould of pedicle valve
(BB . 3o6o4a-b) 10-3 9-4
HORIZON AND LOCALITY. Bod Deiniol Formation, grits in temporary excavation
50 yds. north of Ty-bach Cottage, Bod Deiniol. N.G.R. 37688528.
DISCUSSION. Although a number of pedicle valves were collected, no brachial
valves were found, nor was it possible to examine a thin section of the shell to
determine the nature of the shell material. The fascicostellate ornament, disposition
of the muscle scars and vascula media, and the short median ridge are all found in
Paurorthis. Williams (1962 : 141) has commented on the development of the
latter feature, which is better developed in the allied genus, Cydomyonia.
The valves also show some similarities to certain dalmanellid-like members of
the Orthidae and Finkelnburgiidae. "Pedicle valves of Nanorthis have a similar
shape, with sometimes a fasciculate ornament, but internally the shell is not thick-
ened under the muscle scars; Nothorthis is similar but more transverse. Archae-
orthis also has a Dalmanella-like exterior, but the muscle scars, although elevated,
do not extend forwards from the umbonal cavity as in the Anglesey specimens.
Diparelasma is another dalmanellid-like form, with the muscle scars elevated in a
GEOL. 1 6, 4. 17
158 LOWER PALAEOZOIC BRACHIOPODS
pseudospondylium in front, and a short median ridge, but with a finely costellate
ornament. In many respects the muscle scars and pseudospondylium are very
similar.
Family DALMANELLIDAE Schuchert 1913
Genus DALMANELLA Hall & Clarke 1892
Dalmanella (?) sp.
(PL 5, figs. lo-n)
FIGURED SPECIMENS (measurements in mm.)
Length Width
External mould of brachial valve (BB . 30568) . 8.2 (est)
External mould of pedicle valve (66.30569) . . 7-2 8-4 (est.)
HORIZON AND LOCALITY. Crewyn Formation, grits 420 yds. west-south-west
of Ysgubor-gader. N.G.R. 29589214.
DISCUSSION. The valves are small, and the interiors are very badly preserved,
so that it is impossible to make out the details of the cardinalia in the brachial
valve. Owing to the small size of the brachial valve the ribbing pattern is not
fully developed, so that only the first internal and external branches are developed.
The pedicle valve is deeply convex, and only slightly carinate, the brachial valve
very gently convex with a shallow median sulcus.
Genus ONNIELLA Bancroft 1928
Onniella (?) sp.
(PL 5, figs. 12-14)
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal and external moulds of pedicle valve
(BB.3057oa-b) 8-1
Internal mould of brachial valve (66.30571) . 5-5 6-4
HORIZON AND LOCALITY. Llanbabo Formation, Llanbabo Church Grits, Church
Quarry, Llanbabo. N.G.R. 37758672.
DISCUSSION. The valves are subcircular, biconvex, the pedicle valve having
the greater convexity and the brachial valve a shallow sulcus. The ornament is
only seen on the pedicle valve and is slightly f ascicostellate with forty to fifty costellae
on the margin and a wavelength of 0-23 mm. at 5 mm. from the ventral umbo.
The ventral adductor scar is shorter than, but not enclosed by the diductor scars,
from the ends of which run widely separated and diverging vascula media. The
brachiophores are widely divergent, but the details of the fulcral and supporting
plates are not seen. The former may not be present. The adductor scars in the
brachial valve are quadripartite. The valves recall Onniella (Soudleyella] cf . avelinei
6ancroft (Whittington & Williams 1955 : 407).
AND TRILOBITES OF ANGLESEY 159
Family HARKNESSELLIDAE Bancroft 1928
Genus HARKNESSELLA Reed 1917
Harknessella (?) sp.
(PI. 5, ng. 16)
FIGURED SPECIMEN (measurements in mm.)
Length Width
Exterior of pedicle valve (Af . 1492) . . . . 10 • i 14-7
HORIZON AND LOCALITY. Garn Formation, limestone block in breccia bed,
300 yds. south-east of the summit of Mynydd-y-garn. N.G.R. 31759062.
DISCUSSION. The valve is convex and slightly carinate, with a costellate orna-
ment, no other details can be seen. A carinate pedicle valve is a feature of Hark-
nessella.
Genus HORDERLEYELLA Bancroft 1928
Horderleyella (?) sp.
(PL 5, fig- 15)
FIGURED SPECIMEN. Incomplete internal mould of pedicle valve (66.30572).
HORIZON AND LOCALITY. Llanbabo Formation, Llanbabo Church Grits, Church
Quarry, Llanbabo. N.G.R. 37758672.
DISCUSSION. An internal mould of a pedicle valve from Llanbabo agrees with
Horderleyella? sp. from the Derfel Limestone (Whittington & Williams 1955, pi. 38,
fig. 30) in having similar small subcordate muscle scars, and possibly belonging
to an undescribed species.
Family LINOPORELLIDAE Schuchert & Cooper 1931
Genus SALOPIA Williams 1955
Salopia salteri gracilis Williams
(PL 5, figs. 17-18)
FIGURED SPECIMEN. Incomplete internal mould of brachial valve (66.30573.)
HORIZON AND LOCALITY. Llanbabo Formation, Llanbabo Church Grits, Church
Quarry, Llanbabo. N.G.R. 37758672.
DISCUSSION. The cardinalia and the median septum are well preserved, and
show that the specimens belong to the genus Salopia. Since the cardinalia are
small, with a length of less than 20 per cent, of the valve length, it can be placed
in the subspecies S. salteri gracilis.
i6o LOWER PALAEOZOIC BRACHIOPODS
Family ANGUSTICARDINIIDAE Schuchert & Cooper 1931
Genus RHYNCHORTHIS nov.
DIAGNOSIS. Rostrate biconvex shells, the brachial valve with the greater con-
vexity; rectimarginate or slightly uniplicate; hinge-line narrow; ventral interarea
long and narrow, almost orthocline, delthyrium open; dorsal interarea shorter,
almost orthocline, notothyrium open; ornament on both valves of simple rounded
costae becoming vague towards the flanks.
Ventral interior with receding, almost obsolete dental lamellae; strong teeth,
oval in shape and aligned along the lamellae; orthoid muscle scars, the adductor
and diductor scars expanding forwards, the former not enclosed by the latter.
Dorsal interior with deep notothyrial cavity, cardinal process a simple ridge;
brachiophores plate-like, short and thick, with supporting and socket plates ; adductor
muscle scars orthoid, differentiated into anterior and posterior pairs, the anterior
pair the larger.
TYPE SPECIES. Rhynchorthis rotundus sp. nov. from the Treiorwerth Formation.
DISCUSSION. Schuchert & Cooper (1931 : 244) erected the subfamily Angusti-
cardiniinae, with their new genus Angusticardinia, for orthids evolving towards
the rhynchonellids, but still retaining more orthid characters than those of the
rhynchonellids. Rhynchorthis conforms to the description of the subfamily in
having interareas on both valves, together with both orthid and rhynchonellid
characters. It differs, however, from Angusticardinia in a number of important
features. The interareas, though narrow, are long, the dental lamellae are weak
or obsolete, and there is no median ridge inside the brachial valve. It is not known
whether the shell material of either genus is punctate; Opik (1933 : 5, 6) thought
that Angusticardinia was probably punctate.
Apatorthis (Opik 1933 : 5, from the middle and upper Ordovician of Estonia)
is another rhynchonelliform shell, but has short and narrow curved interareas of
equal length, a well marked fold and sulcus, and angular costae. The shell is
punctate and is placed by Opik in the Enteletacea.
Schuchert & Cooper (1932 : 84) suggested that Angusticardinia, being 'the earliest
rhynchonelliform shell known', may have been the ancestor of the rhynchonellids,
evolving into Rhynchotrema. Rhynchorthis is contemporary with Angusticardinia,
but seems to be closer in structure to the ancestral orthids. The hinge-line is
not quite so narrow, the interareas are long, and the cruralium-like structure of
Angusticardinia, in which the supporting plates meet a median ridge, is not developed.
Rhynchorthis rotundus gen. et sp. nov.
(PI. 5, figs. 19-26)
DIAGNOSIS. Species of Rhynchorthis, six-fifths as long as wide, dorsi-biconvex
with brachial valve one-fifth as deep as long, pedicle valve one-eighth as deep as
long, ornamented by about twelve simple costae; internal details as for genus.
AND TRILOBITES OF ANGLESEY
161
TYPE SPECIMENS (measurements in mm.)
Length Width
HOLOTYPE.
Internal
mould
of
brachial
valve
(BB
30551)
PARATYPES.
Internal
mould
of
brachial
valve
(BB
30552)
Internal
mould
of
brachial
valve
(BB
30553)
Internal
mould
of
pedicle
valve
(BB
30554)
Internal
mould
of
pedicle
valve
(BB
10-1
8-4
ii-l
12-4
9'5
30556)
TYPE HORIZON AND LOCALITY. Treiorwerth Formation, sandstones 300 yds.
south-east of Ffynnon-y-mab, Trefor. N.G.R. 36247950.
DISCUSSION. The new species is known from a number of rather poorly preserved
moulds, particularly so in the case of the external moulds. The mean length per
cent, of 5 pedicle valves relative to the width is 121-0 (variance 195-0). The cor-
responding figures for 5 brachial valves are 107-4 and 121-5. In the five brachial
valves the mean depth per cent, relative to length is 20-6 (variance 29-2).
Suborder CLITAMBONITIDINA Opik 1934
Superfamily CLITAMBONITACEA Winchell & Schuchert 1893
Family POLYTOECHIIDAE Opik 1934
Genus TRITOECHIA Ulrich & Cooper 1936
Tritoechia sp.
(PI. 6, figs. 1-3, 5)
FIGURED SPECIMEN (measurements in mm.)
Length Width
Internal and external moulds of pedicle valve
(BB . 30557a-b) 17-0 19-8 (est.)
HORIZON AND LOCALITY. Treiorwerth Formation, sandstones 300 yds. south-
east of Ffynnon-y-mab, Trefor. N.G.R. 36247950.
DISCUSSION. Only one well preserved pedicle valve, the figured specimen, and
a few other poorly preserved pedicle valves have been found. No brachial valves
have been found which can definitely be assigned to the genus.
The valve conforms externally to the genus Tritoechia. In outline it is semi-
circular, widest at the hinge-line, with cardinal angles just acute. The surface is
evenly convex, the umbo not incurved or inflated, and the interarea plane, apsacline
but almost catacline. The delthyrium is covered by a strongly convex deltidium,
but the foramen is not preserved. The ornament, which is poorly preserved, is
finely multicostellate, with about fourteen costellae in 5 mm. both at the margin
i62 LOWER PALAEOZOIC BRACHIOPODS
and near the umbo. Internally the teeth are strong and rounded, supported by
receding dental lamellae which diverge ventrally. The form and extent of the
muscle scars are not known.
Among the species of Tritoechia described by Ulrich & Cooper (1938 : 162-169)
are a number which approach the valve closely, the nearest being T. transversa,
which has an interarea more inclined towards the orthocline.
Family CLITAMBONITIDAE Winchell & Schuchert 1893
Subfamily CLITAMBONITINAE Winchell & Schuchert 1893
Genus CLITAMBONITES Pander 1830
Clitambonites (?) sp.
(PL 6, fig. 4)
FIGURED SPECIMEN. Fragmentary external mould of brachial valve (66.30558).
HORIZON AND LOCALITY. Llanbabo Formation, Llanbabo Church Grits, Church
Quarry, Llanbabo. N.G.R. 37758672.
DISCUSSION. The external mould is of a large, probably subquadrate brachial
valve in excess of 18 mm. long by 26 mm. wide, gently convex, becoming flat or
slightly sulcate medianly. The ornament is mulitcostellate, with perhaps four
costellae per cm. at 5 mm. from the umbo, and at the margin eighteen per cm.
At least ten more prominent ribs divide the ornament into sectors, each with four
to six smaller ribs, arising both by implantation and bifurcation. Strong thick
growth lamellae occur at intervals. The convex shape, and prominent growth
lamellae, are both features of Clitambonites. Clinambon and Vellamo both have
much less prominent growth costellae.
Genus ILMARINIA Opik 1934
Ilmarinia sp.
(PL 6, figs. 6-7)
FIGURED SPECIMEN. Internal and external moulds of incomplete pedicle valve
(BB.3o559a-b).
HORIZON AND LOCALITY. Llanbabo Formation, Llanbabo Church Grits, Church
Quarry, Llanbabo. N.G.R. 37758672.
DISCUSSION. Two counterpart moulds of the pedicle valve of a clitambonitaceid
from Llanbabo show a subquadrate outline, a long apsacline interarea, and a slight
sulcus. The delthyrium is possibly open, or constricted by deltidial plates, because
there are certainly traces of a large foramen, and the ornament is finely multicostellate.
Internally there is a good spondylium, one-third the width of the valve, and elevated
by its own depth from the floor of the valve. It has a flat floor, and (though the
specimen is broken) shows what may be the beginning of a thin receding median
septum. Ilmarinia is the only clitambonitaceid genus with a ventral sulcus, and
hence the specimen probably belongs here.
AND TRILOBITES OF ANGLESEY 163
Subfamily ATELELASMATINAE Cooper 1956
Genus APOMATELLA Schuchert & Cooper 1931
Apomatella (?) sp.
(PI. 6, figs. 8-n)
DESCRIPTION. Pedicle valve subquadrate, wider than long, widest at the hinge-
line with the cardinal angles right angles; deeply pyramidal, slightly flattened
medianly, interarea catacline or strongly apsacline, slightly curved, twice as wide
as long ; delthyrium probably open ; ornament finely costellate ; spondylium simplex
high, shallow in cross-section; median septum receding.
FIGURED SPECIMENS (measurement in mm.)
Length Width
Internal and external moulds of pedicle valve
(BB.3o6o5a-b) 8-8
Internal and external moulds of pedicle valve
(BB . 3o6o6a-b) . . . . . . 10-9 I3'4(est.)
HORIZON AND LOCALITY. Bod Deiniol Formation, Grits in temporary excavation
50 yds. north of Ty-bach Cottage, Bod Deiniol. N.G.R. 37688528.
DISCUSSION. A number of pedicle valves have been found at this locality, none
with any trace of plates restricting the delthyrium, suggesting that the absence
of plates is more than an accident of preservation.
Superfamily GONAMBONITACEA Schuchert & Cooper 1931
Family GONAMBONITIDAE Schuchert & Cooper 1931
Subfamily GONAMBONITINAE Schuchert & Cooper 1931
Genus ANTIGONAMBONITES Opik 1934
Antigonambonites pyramidalis sp. nov.
(PL 6, figs. 12-18)
DIAGNOSIS. Outline sub-rectangular, wider than long, hinge-line just less than
maximum width, anterior and lateral commissures rectimarginate ; biconvex,
pedicle valve pyramidal, with a long almost catacline interarea, slightly curved,
brachial valve slightly convex, with a shallow median sulcus, interarea short and
anacline; delthyrium probably closed or restricted by convex deltidial plates;
notothyrium restricted but not closed by chilidial plates; ornament costellate,
costellae numbering four per mm. at 5 mm. from the umbo, stronger ribs appearing
at intervals, ribs crossed by well marked growth lines giving a slightly imbricate
appearance; teeth not seen in ventral interior, but muscle scars impressed on a
largely sessile spondylium triplex, supported at its anterior end by two lateral septa,
the median septum being almost obsolete, adductor and diductor scars expanding
forwards, the adductor tracks separated from the diductor tracks by raised ridges ;
dorsal interior with brachiophores long and widely divergent, measuring between
164
LOWER PALAEOZOIC BRACHIOPODS
their tips over half the width of the valve, median septum very short or absent,
cardinal process simple ; adductor muscle scars within a semicircular track bounded
by the brachiophores and by an indented ridge; margin crenulated.
TYPE SPECIMENS (measurements in mm.)
Length Width
HOLOTYPE. Internal and external moulds of brachial
valve (BB.3056ia-b) . . . . 5-8 7-5
PARATYPES. Internal mould of pedicle valve (BB.
30562)
Internal mould of brachial valve (B . 30563) 9 • 9
Internal mould of pedicle valve (BB.
30564) 6-8
TYPE HORIZON AND LOCALITY. Treiorwerth Formation, sandstones 300 yds.
south-east of Ffynnon-y-mab, Trefor. N.G.R. 36247950.
DISCUSSION. The poor preservation of the specimens, and the fact that they
are preserved as natural moulds and not as complete specimens with the original
shell material, means that it is impossible to study the form and structure of the
spondylium in detail. Since, however, it is a spondylium triplex the specimens
belong to the Gonambonitidae. Antigonambonites Opik is the closest described
genus, being biconvex and having a largely sessile spondylium. The described
species are generally flatly lenticular, with an apsacline interarea in the pedicle
valve. The ornament is similar to that of A. costatus Opik (1934 : 156), in which
the costellae are conspicuous and angular, though in this species some costellae are
accentuated. The pedicle valve is also deeper, in shape like that of Skenidioides ,
and has a similarly inclined interarea. The deltidial plates are poorly preserved
in the moulds, and it is impossible to say whether they meet medianly or not. The
mean percentage length relative to width of 5 brachial valves is 76-0, with a range
from 58-2 to 92-9.
Genus ESTLANDIA Schuchert & Cooper 1931
Estlandia (?) sp.
(PI. 7, figs. 2-4, 6-9)
1919 Petraia sp. Greenly : 435.
FIGURED SPECIMENS (measurements in mm.)
Internal and external moulds of incomplete pedicle
valve (Af. 238, Af. 225)
Internal mould of brachial valve (Af .214)
Internal and external moulds of brachial valve
(BB.3056oa-b)
Length Width
5'4
distorted
HORIZON AND LOCALITY. Berw-uchaf Grits, 90 yds. north of Bwlch-gwyn farm,
Holland Arms. N.G.R. 48207303.
AND TRILOBITES OF ANGLESEY 165
DISCUSSION. The pedicle valve is strongly pyramidal, with a long apsacline
interarea, possibly with an open delthyrium and with a costellate surface, the
costellae having the 'chain-sculpture' characteristic of Estlandia. The interior
has a well developed spondylium triplex, with a thick median septum, and thinner
lateral septa parallel to the median septum. The interior of the brachial valve
has long widely divergent brachiophores, thickened at their outer ends. The
adductor muscle scars are half the length of the valve, pentagonal in form, with
crenulated antero-lateral margins. They are separated by a thin median septum
which joins the brachiophores at their inner ends to form an anchor-shaped structure.
The valves are provisionally placed in Estlandia as the ornament of the pedicle
valve is quite characteristic of that genus. The side septa of Estlandia, however,
are usually short and widely spaced, rather than close to the median septum.
Family KULLERVOIDAE Opik 1934
Genus KULLERVO Opik 1932
Kullervo aff. panderi (Opik)
(PI. 6, figs. 19-22; PI. 7, fig. i)
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal mould of pedicle valve (BB . 30565) . . distorted
Internal mould of pedicle valve (BB . 30566) . . 3-3 7-5
Internal and external moulds of brachial valve
(BB.3o567a-b) 4-5 8-5
HORIZON AND LOCALITY. Llanbabo Formation, Llanbabo Church Grits, Church
Quarry, Llanbabo. N.G.R. 37758672.
DISCUSSION. The specimens are certainly conspecific with Kullervo aff. panderi
(Opik) described by Williams (Whittington & Williams 1955 : 412, pi. 30, figs.
56-62) and, like it, differ from Opik's species only in the poorer development of the
hemi-syrinx. The cardinal angles are slightly alate, and on them the concentric
ornament is more pronounced than medianly (cf. Opik 1934 text-fig. 37). The
ventral interarea is almost catacline and appears to have an open delthyrium;
since the specimens are small this is probably a characteristic of young stages, as
suggested by Williams (Whittington & Williams 1955 : 412). There are no sub-
spondylial septa.
Suborder CLITAMBONITIDINA Opik 1934
Superfamily and genus uncertain
(PI. 7, figs. 5, lo-n)
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal mould of pedicle valve (BB . 30607) .
Internal and external moulds of brachial valve
(BB.3o6o8a-b) 8-0 14-6
166 LOWER PALAEOZOIC BRACHIOPODS
HORIZON AND LOCALITY. Bod Deiniol Formation, grits in temporary excavation
50 yds. north of Ty-bach Cottage, Bod Deiniol. N.G.R. 37688528.
DISCUSSION. Two valves found in the Nantannog Beds at the site of the Alaw
reservoir cannot be assigned to any clitambonitid species. In particular it is not
certain whether they belong together. The pedicle valve has a very long interarea,
with deltidial plates, dental lamellae which converge to the floor of the valve,
possibly with side septa, and with a prominent central groove in the floor of the
delthyrium; the ornament is coarsely costellate. If the structure is a spondylium
simplex then the valve may belong to the Polytoechiidae, as the median septum
seems only to be rudimentary. The brachial valve is quadrate in outline, slightly
alate, convex with a shallow median sulcus, and a short, almost orthocline interarea,
possibly with a small chilidium; the ornament is coarsely costellate and imbricate.
Internally the cardinalia are elevated on a notothyrial platform, which passes into
a broad median septum ; the cardinal process is a simple ridge, with widely divergent
socket ridges; the muscle scars have two pairs of septa lying lateral to them, parallel
to the median septum.
Order STROPHOMENIDA Opik 1934
Suborder STROPHOMENIDINA Opik 1934
Superfamily PLECTAMBONITACEA Jones 1928
Family PLECTAMBONITIDAE Jones 1928
Subfamily AHTIELLINAE Opik 1933
Genus AHTIELLA Opik 1932
Ahtiella quadrat a sp. nov.
(PL 8, figs. 1-9)
DIAGNOSIS. Alate, subrectangular Ahtiella, two-thirds as long as wide; brachial
valve convex, with a median sulcus widening and deepening anteriorly, flanked
by rounded folds and slightly concave flanks near the cardinal angles; anterior
commissure bent ventrally in some specimens; interarea anacline, notothyrium
possibly covered by a small convex chilidium at its apex; pedicle valve flat or
concave, with a low carinate median fold, and the anterior and lateral commissures
bent ventrally; delthyrium open, possibly covered by a small arched plate at its
apex; interarea strongly apsacline, eight times as wide as long; ornament of about
fifteen costellae in 5 mm. at 5 mm. from the ventral umbo, every third or fourth
costella accentuated, pedicle valve with about three very oblique and indistinct
wrinkles near the cardinal angles; teeth angular, aligned along the hingeline, sup-
ported by very short receding dental lamellae diverging to the floor of the valve;
muscle scars rectangular, wider than long, adductor scars not enclosed by diductor
scars, both pairs expanding linearly forwards, adductors enclosing an angle of 60°
with an arcuate anterior margin, diductors blade-like, extending beyond the ad-
ductors, enclosing an angle of 75° between their outer margins; small depressions
AND TRILOBITES OF ANGLESEY 167
beneath teeth are either pedicle adjuster scars or depressions to accommodate the
socket ridges ; two pairs of vague ridges radiate from the ends of the diductor scars ;
anterior and lateral margins abruptly deflected ventrally ; cardinalia orthid, elevated
on a notothyrial platform; cardinal process a simple ridge, thickened along its
anterior edge, highest midway along its length and triangular in outline; socket
ridges short and rod-like, diverging at about 90°, resting directly on the notothyrial
platform and possibly continuous with an incipient chilidium ; sockets broad excava-
tions in the hinge-line, diverging at about 90° and each enclosing an angle of 20°;
prominent median septum separating the muscle scars, which are disposed in an
arc about the umbo, extending just less than half the length of the valve, one pair
lateral to the other.
TYPE SPECIMENS (measurements in mm.)
Length Width
HOLOTYPE. Internal mould of pedicle valve (66.30609) 10-9 15 -8
PARATYPES. Internal mould of pedicle valve (BB.
30610) . . . . . . 13-3 21-2 (est.)
Internal and external moulds of pedicle
valve (BB.3o6na-b) ... 22-0 (est.)
Internal and external moulds of brachial
valve (BB . 3o6i2a-b)
Internal and external moulds of brachial
valve (BB . 3o6i3a-b)
Internal and external moulds of brachial
valve (BB . 3o6i4a-b)
TYPE HORIZON AND LOCALITY. Torllwyn Formation, sandstones 50 ft. above
the base of the succession on the north side of the faulted syncline, 45 yds. north
of Ogof Gynfor, Llanbadrig. N.G.R. 37859490.
Ahtiella concava sp. nov.
(PI. 7, figs. 12-22)
DIAGNOSIS. Semicircular slightly alate Ahtiella, six-tenths as wide as long;
brachial valve evenly convex in lateral view, with a narrow median sulcus having
a V-shaped cross-section, flanked by rounded folds; interarea anacline to almost
orthocline, very short, notothyrium possibly covered by a small convex chilidium
at its apex; pedicle valve convex in lateral view, becoming more strongly bent
towards the anterior commissure, but with the convexity broken by a narrow
carinate fold which becomes more rounded and vaguer away from the umbo; del-
thyrium covered by a small arched plate at its apex; interarea procline or catacline,
one-thirteenth as long as wide; ornament on both valves too fine to be observed,
but growth lines present near the margins of valves; teeth triangular, aligned along
the hinge-line, supported by very short receding dental lamellae diverging to the
floor of the valve; muscle scars rectangular, diductors extending further forwards
1 68
LOWER PALAEOZOIC BRACHIOPODS
than adductors, but details not seen; vague ridges radiating from the diductor
scars; anterior and lateral margins deflected ventrally in some specimens; dorsal
cardinalia orthid, elevated on a notothyrial platform; cardinal process a simple
ridge, triangular in side view and thickened along its anterior margin; socket ridges
short and rod-like, diverging at 90°, sockets shallow excavations under the hinge-
line; muscle scars separated by a prominent median septum, posterior scars rounded
and set in excavations under the notothyrial platform, anterior scars elongate and
lying along each side of the median septum, extending to almost half the length
of the valve, flanked by three ridges on each side, radiating from the posterior
scars; median septum cusp-shaped in lateral outline, highest at its mid-point,
thickened and swollen in its anterior half.
TYPE SPECIMENS (measurements in mm.)
HOLOTYPE. Internal and external moulds of pedicle
valve (BB . 3o6i5a-b)
PARATYPES. Internal and external moulds of brachial
valve (BB . 3o6i6a-b)
Length Width
17-2 23-8
(distorted)
19-8
(distorted)
13-0 20-7 (est.)
n-7
22-2
Internal and external moulds of brachial
valve (BB . 3o6i7a-b)
Internal and external moulds of brachial
valve (BB.3o6i8a-b)
Internal and external moulds of pedicle
valve (BB.3o6i9a-b)
(distorted)
TYPE HORIZON AND LOCALITY. Bod Deiniol Formation, grits in temporary
excavation 50 yds. north of Ty-bach Cottage, Bod Deiniol. N.G.R. 37688528.
DISCUSSION. The two Anglesey species of Ahtiella differ from each other mainly
in external shape and ornament, and in the development of the internal ridges
in the brachial valve. A. quadmta has a rectangular outline, with the pedicle
valve almost flat across the visceral disc and the brachial valve gently convex;
both fold and sulcus are shallow. The ventral interarea is apsacline, and the orna-
ment unequally costellate. In contrast A. concava is semicircular in outline, the
pedicle valve has a concave visceral disc, and the brachial valve is strongly convex ;
both fold and sulcus are carinate, and higher and deeper. The ventral interarea
is procline to catacline, and the ornament, though not preserved, is probably much
finer.
Both species differ in their combinations of characters from the Baltic species
described by Cpik (1932; 1933) and Hessland (1949). Most of these are relatively
much wider, with prominent rugae close to the hinge-line. The fold and sulcus
of A. concava are much better developed than in any Baltic species, although in
outline and covexity it is similar to A. lirata Opik. A. quadrata is more quadrate
than any of the Baltic forms, and less convex.
AND TRILOBITES OF ANGLESEY 169
The mean percentage of length relative to width of five pedicle valves of A.
quadrata was 64-7 (range 57'3~^9*°)' For A. concava the corresponding value for
thirteen pedicle valves was 59-8 (range 51 7-77 -o) and for eight brachial valves
62-1 (range 54-9-78-4). Correlation coefficients between length and width for
these specimens were not significant, due to poor preservation and distortion of
the specimens. For similar reasons it was not possible to make any accurate
estimate of the thickness of the valves.
Genus REINVERSELLA nov.
DIAGNOSIS. Semicircular plectambonitaceans with small postolateral wings;
abruptly geniculate, with the border deflected ventrally ; ventral disc convex, dorsal
disc flat, the anterior and lateral commissures with a frill or gutter deflected dorsally ;
ventral interarea apsacline, short and wide, dorsal interarea short, anacline, both
delthyrium and notothyrium open; ornament of fine bifurcating costellae, crossed
by irregular concentric rugae on the visceral disc.
Ventral interior with dental lamellae diverging widely both laterally and ventrally,
continuous with low ridges round the muscle scars; muscle scars triangular, adduc-
tor and diductor scars equal in length.
Dorsal interior with cardinalia raised on a low notothyrial platform; cardinal
process low, thin and blade-like, slightly swollen anteriorly; brachiophores short
and triangular in section, continuous on their ventral faces with the interarea.
TYPE SPECIES. Reinversella monensis sp. nov. from the Treiorwerth Formation.
DISCUSSION. This genus is separated from Inversella Opik because of the develop-
ment of a second deflection of the anterior and lateral borders of the shell, which
forms a sort of frill or gutter. A similar, but more elaborate frill is characteristic
of Limbimurina Cooper (1956 : 851-852), which bears the same relationship to the
strophomenacean Leptaena as the new genus does to Inversella. Two of the des-
cribed species of Inversella, I. borealis Opik and /. angulata Opik, have a chilidium,
and it may be present in the third species /. perundosa Opik. In contrast the
new genus has an open notothyrium.
Reinversella monensis gen. et sp. nov.
(PI. 8, figs. 10-17)
1919 Leptaena rhomboidalis (Wilckens), partim.; Matley in Greenly : 442.
DIAGNOSIS. A species of Reinversella three-quarters as wide as long, and about
one-third as deep as wide, ornamented with fine bifurcating costellae numbering
fourteen to seventeen per 5 mm. on the rim of the visceral disc, crossed by seven
to nine rugae, continuous or anastomosing across the midline ; in the ventral interior
the width of the muscle scars is about one-fifth the width of the valve and their
length one-quarter the length of the valve; the width of the cardinalia is one-fifth
the width of the brachial valve.
170 LOWER PALAEOZOIC BRACHIOPODS
TYPE SPECIMENS (measurements in mm.)
Length Width
HOLOTYPE. External and internal moulds of brachial
valve (BB . 30574a-b) .
PARATYPES. External and internal moulds of pedicle
valve (BB . 30575a-b)
External and internal moulds of brachial
valve (BB.30576a—b) . . .
15-3 21-3
(distorted)
15-5 i8-o(est.)
TYPE HORIZON AND LOCALITY. Treiorwerth Formation, sandstones 300 yds.
south-east of Ffynnon-y-mab, Trefor. N.G.R. 36247950.
DISCUSSION. In addition to bearing a frill, the new species shows detail differences
from the described species of Inversella. I. perundosa Opik from the Expansus-
schiefer, D. hirundo zone (Opik 1939 : 128, 142, PL 5, fig. 6) is the closest species,
but has a prominent broad median costella.
Family LEPTESTIIDAE Opik 1933
Subfamily LEPTESTIINAE Opik 1933
Genus PALAEOSTROPHOMENA Holtedahl 1916
Palaeostrophomena sp.
(PI. 9, figs. 2, 4-5)
FIGURED SPECIMENS (measurements in mm.)
Internal and external moulds of pedicle valve
(BB.3o579a-b)
Internal mould of brachial valve (BB . 30580)
Length Width
7-6
HORIZON AND LOCALITY. Llanbabo Formation, Llanbabo Church Grits, Church
Quarry, Llanbabo. N.G.R. 37758672.
DISCUSSION. The pedicle valve is subquadrate, and gently convex. The orna-
ment consists of fine costellae, divided into sectors each containing five to seven
costellae separated by stronger costellae numbering about thirty. Internally there
appear to be no dental lamellae, other details have been obliterated. The brachial
valve shows the cardinalia, the cardinal process is a rounded mass (as preserved)
passing into a median septum, the sockets and accessory sockets are conspicuous.
The specimens agree in all visible details with P. magnified Williams, but the form
of the ventral muscle scars, one of the diagnostic features of that species, is not
visible in the Llanbabo specimens.
AND TRILOBITES OF ANGLESEY 171
Palaeostrophomena (?) sp.
(PL 9, %. i)
FIGURED SPECIMEN (measurements in mm.)
Length Width
Exterior of pedicle(?) valve (BB.3058ia-b) . . 11-7 24-0 (est.)
HORIZON AND LOCALITY. Garn Formation, limestone blocks in breccia beds,
Forth Padrig, Mynachdy. N.G.R. 30539279.
DISCUSSION. The valve is semicircular and gently convex. The posterior
margin forms a slight angle at the umbo, the cardinal angles are acute, produced
into small wings, and the lateral and anterior margins evenly curved. The ornament
is of fine parvicostellae, separated into sectors containing sixteen in each by sharp
accentuated costellae, about twelve in number in the whole valve, all the costellae
arising by implantation. The surface of the valve is wrinkled along the posterior
margin by radial rugae, which are more faintly developed over the whole surface.
The valve cannot be closely compared with Palaeostrophomena sp., as the interior
is not exposed, but it agrees with the genus in exterior details. The closest species
is P. magnifica Williams, though the number of parvicostellae in each sector is
different. It could also belong to Glyptambonites Cooper, in which the pedicle
valve has the same outline, convexity and ornament.
Family LEPTELLINIDAE Ulrich & Cooper 1936
Subfamily LEPTESTIININAE Havlicek 1961
Genus LEPTESTIINA Havlicek 1952
Leptestiina derfelensis (Jones)
(PL 9, figs. 7-9)
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal mould of pedicle valve (BB . 30577) . . 4-8
Internal mould of brachial valve (66.30578)
HORIZON AND LOCALITY. Tandinas Shales, by the track 50 yds. west of Tandinas
quarry, Careg-onen. N.G.R. 58248187.
DISCUSSION. Both valves show the internal characters well, particularly the
brachial valve, in which the cardinalia and the lophophore platform are perfectly
preserved. The papillae are not visible in the pedicle valve.
Genus BILOBIA Cooper 1956
Bilobia aff. musca (Opik 1930)
(PL 9, figs. 10-13)
DESCRIPTION. Triangular Bilobia with rounded cardinal angles and an anterior
tongue, four-fifths as long as wide; the brachial valve evenly concave and the
\-/i LOWER PALAEOZOIC BRACHIOPODS
pedicle valve slightly carinate with flattened flanks; teeth double, the posterolateral
pair the larger; dental lamellae divergent, continuous with a raised rim to the
muscle scars which is indented medianly in a right angle; diductor scars large and
flabellate with small auxiliary lobes under the teeth, possibly just meeting anterior
to the adductor scars and extending one-third the length of the valve; vascula
media converging anteriorly from the ends of the diductor scars ; dorsal lophophore
platform prominent, one-half the length of the valve, elevated and free anteriorly,
markedly bilobed with each lobe rounded.
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal mould of pedicle valve (BB . 30582) . . 10-3 10-6
Internal mould of brachial valve (BB . 30583)
HORIZON AND LOCALITY. Llanbabo Formation, Llanbabo Church Grits, 180
yds. east of Fferam-uchaf, Llanbabo. N.G.R. 36548673.
DISCUSSION. The pedicle valve is very similar to that of Bilobia musca (Opik)
in the general shape, the form of the teeth, and the muscle scars. In the brachial
valve the lophophore platform has similar rounded anterior lobes. None of the
specimens shows the cardinalia, and there are no external moulds well enough
preserved to show the ornament.
Family SOWERBYELLIDAE Opik 1930
Subfamily SOWERBYELLINAE Opik 1930
Genus EOPLECTODONTA Kozlowski 1929
Eoplectodonta lenis Williams
(PL 9, figs. 14-18)
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal and external moulds of pedicle valve
(BB.3o584a-b)
Internal and external moulds of brachial valve
(BB.3o585a-b) . . 5-7
External mould of brachial valve with interarea of
pedicle valve (BB . 30586) ....
HORIZON AND LOCALITY. Llanbabo Formation, Llanbabo Church Grits, Church
Quarry, Llanbabo. N.G.R. 37758672.
DISCUSSION. The interior of the pedicle valve conforms to that of E. lenis from
the Derfel Limestone, though the denticles are only poorly seen on the right side.
The dorsal muscle scars are raised on low platforms, and are flabellate in form
with one pair outside the other. The median and submedian septa are almost
parallel, and between the scars are distinct depressions running their full length.
AND TRILOBITES OF ANGLESEY 173
Subfamily PTYGHOGLYPTINAE Cooper 1956
Genus PTYCHOGLYPTUS Willard 1928
Ptychoglyptus sp.
(PI. 10, figs. 1-2)
DESCRIPTION. Pedicle valve semicircular, slightly alate, gently convex; brachial
valve concave medianly with flattened wings; ornament divided into sectors by
sharp accentuated costae and costellae, 8 at the margin of valve 4 mm. long, possibly
three primary, the others arising about 1-5 mm. from the umbo; between are fine
parvicostellae, too poorly preserved to be counted; concentric ornament of prominent
rugae, faint at less than 2mm. from the umbo, slightly asymmetrical in cross section,
steeper towards the umbo; divided into sectors by the sharp costellae which they
do not cross or fold, in the median part of the valves alternating between them,
laterally tending to coincide across them, bent convex to the umbo; fine concentric
growth lines follow the rugae, hence the valve margin is scalloped.
FIGURED SPECIMENS (measurements in mm.)
Length Width
Exterior of pedicle valve (BB . 30590) . . . 4-4
Exterior of brachial valve (BB . 30589) .
HORIZON AND LOCALITY. Garn Formation, limestone blocks in breccia beds,
Porth Padrig, Mynachdy. N.G.R. 30539279.
DISCUSSION. The valves are all small, none being above 5 mm. long; since most
described members of the genus are up to four times this length it is possible that
these are all young specimens, not affording adequate material upon which to erect
a new species. Ptychoglyptus kindlei Cooper (1956 : 816) appears similar, but
grows to a much larger size and develops a geniculation. P. virginiensis Willard
(Cooper 1956 : 818) is also similar though the rugae seem to become prominent at
an earlier growth stage. P. valdari (Spjeldnaes 1957 : 58; Williams 1962 : 194)
has rugae with both faces sloping anteriorly, with the posterior face undercut, and
this is also true of P. cf. valdari from Girvan (Williams 1962 : 194). P. cf. virgini-
ensis, also from Girvan (Williams 1962 : 193), has similar rugae and costae, and
is Caradoc in age.
Subfamily AEGIROMENINAE Havlicek 1961
Genus SERICOIDEA Lindstrom 1953
Sericoidea abdita Williams
(PL 9, figs. 3, 6)
FIGURED SPECIMENS (measurements in mm.)
Length Width
Interior of brachial valve (BB . 30587) . . . 1-7
Interior mould of brachial valve with shell material
adhering (BB . 30588)
GEOL. l6, 4. iS
i74 LOWER PALAEOZOIC BRACHIOPODS
HORIZON AND LOCALITY. Tandinas shales, on the shore by the powerhouse 100
yds. west of the pier, Careg-onen. N.G.R. 58208193.
DISCUSSION. Specimen 66.30587 shows the pattern of septules characteristic
of this species, three pairs of lateral septules and a narrow, more prominent median
septule. 66.30588 shows the cardinalia but is not complete enough to show the
septules.
Superfamily STROPHOMENACEA King 1846
Family LEPTAENIDAE Hall & Clarke 1892
Genus LEPTAENA Dalman 1828
Leptaena sp.
(PL 10, figs. 3-6)
DESCRIPTION. Outline semicircular, slightly auriculate; pedicle valve with con-
cave visceral disc bounded by a sharply raised ridge passing to a sharp geniculation ;
interarea apsacline, extending the width of the valve and about one-fifteenth as
long as wide, delthyrium enclosing an angle of about 135°, open, pseudodeltidium
not observed; brachial valve with flat visceral disc, bounded by rounded depression
before the geniculation; interarea narrower than on the pedicle valve; notothyrium
covered by a conspicuous convex chilidium with a median depression; interior of
pedicle valve with teeth as narrow outgrowths from the hinge-line, elongated
parallel to it, dental lamellae not seen, muscle scars elliptical in outline, with lance-
olate adductor scars enclosed by diductors, the latter separated by a septum an-
teriorly; brachial interior with bilobed cardinal process tapering forwards to a
point, the outer edges parallel and the inner ones diverging at 60°, sockets bounded
by vague ridges forming the posterior edge to the muscle scars and uniting with a
low median ridge to produce an anchor-like structure, with the median ridge passing
into a short sharp median septum just before the edge of the disc, which is raised
and crossed at intervals by radial grooves.
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal mould of pedicle valve (66.30591) . . 10-3 19-6 (est.)
Internal mould of brachial valve (66 . 30592)
Internal mould of brachial valve (66 . 30593)
HORIZON AND LOCALITY. Llanbabo Formation, Llanbabo Church Grits, 180
yds. east of Fferam-uchaf, Llanbabo. N.G.R. 36548673.
DISCUSSION. The material compares well with that from the Derfel Limestone
(Whittington & Williams 1955 : 419, pi. 39, figs. 86-90). There is no septum
preserved between the lobes of the cardinal process in the Angelsey specimens,
and their exteriors are unknown.
AND TRILOBITES OF ANGLESEY 175
Genus DACTYLOGONIA Ulrich & Cooper 1942
Dactylogonia sp.
(P. 10, figs. 7-8)
DESCRIPTION. Brachial valve incomplete, broken along a growth line, possibly
along a line of geniculation ; slightly concave in longitudinal view, almost plane in
anterior view; outline semi-circular, slightly alate, hinge-line straight, the greatest
width; interarea very short, wide, anacline, notothyrium apparently lacking a
chilidial cover; ornament of very faint concentric rugae, developing at about 3
mm. from the umbo, costellae if present too fine to be preserved; cardinal process
short, bilobed, uniting with a low median ridge that bifurcates anteriorly; socket
ridges diverging at 110° to each other, adpressed to the valve surface, bounding
sockets which are not raised above the general interior; muscle scars bounded by
a series of septa, two prominent sub-median septa parallel to each other becoming
thickened and diverging at their posterior ends, separated by a slot from low thick
diverging septa, which are separated from the socket ridges by a narrow depression ;
anterior ends of the sub-median septa separated by two triangular raised areas,
between which is a thin median septum; inner surface outside the septa covered
by a series of coarse pustules.
FIGURED SPECIMEN. Internal and external moulds of an incomplete brachial
valve (BB.3o596a-b).
HORIZON AND LOCALITY. Nantaiinog Formation, fine sandstones and shales
190 yds. south-east of Fferam-uchaf, Llanbabo. N.G.R. 36518657.
DISCUSSION. Without more material it is impossible to place this specimen
more exactly. The pattern of septa recalls those of Dactylogonia (cf. Cooper 1956 :
pi. 225, fig. 4), though the septa here are nearer the socket ridges, and are separated
only by narrow slots. The three pairs of raised areas together form a rim, locating
within it the visceral mass of the animal. The slots between the septa were probably
for the passage of the various vascula, the vascula media between the anterior pair,
and the vascula myaria posterior to the long prominent pair. The inner margins of
the two pairs of septa slope obliquely inwards, and are probably the seats of attach-
ment of the adductor muscle scars.
? Dactylogonia sp. has been described by MacGregor (1961 : 204) from the upper
Llandeilo of the Berwyn mountains. His specimen does not greatly resemble
that described above, the septa being weakly developed, the cardinal process large,
and the pustules less distinct and drawn out radially.
Genus KI AERO MEN A Spjeldnaes 1957
Kiaeromena (?) sp.
(PI. 10, figs. 9, 10)
FIGURED SPECIMENS. Exterior of incomplete pedicle(?) valve (66.30594).
Exterior of incomplete brachial(P) valve (66.30595).
176 LOWER PALAEOZOIC BRACHIOPODS
HORIZON AND LOCALITY. Garn Formation, limestone blocks in breccia bed,
Forth Padrig, Mynachdy. N.G.R. 30539279.
DISCUSSION. The valves are semicircular, slightly alate and geniculate, and as
neither the hinge-lines and interareas nor the interiors are preserved the valves
have been determined on their transverse profile and ornament. The pedicle
valve is convex, with the disc slightly carinate along the midline, the brachial valve
with a slightly concave disc. The ornament on both valves is of fine parvicostellae,
approximately ten per mm. on the valve margins, divided into sectors by stronger
costellae, of which six arise near the umbo and fifteen are present at the margin
of a valve about 9 mm. long. Both types of ribs arise by implantation. There
are no rugae on the disc.
Order PENTAMERIDA Schuchert & Cooper 1931
Suborder SYNTROPHIIDINA Ulrich & Cooper 1936
Superfamily PORAMBONITACEA Davidson 1853
Family HUENELLIDAE Schuchert & Cooper 1931
Subfamily RECTOTROPHIINAE nov.
Globular huenellids with parallel dental lamellae, and with parallel supporting
plates in the brachial valve, without cardinal process.
Genus RECTOTROPHIA nov.
DIAGNOSIS. Globular subtriangular biconvex shells with deep pedicle valve and
less convex brachial valve, rectimarginate commissure and narrow hinge-line;
ornament unknown.
Ventral interior with parallel dental lamellae, the muscle scars confined between
them and elevated on a low pseudospondylium.
Dorsal interior with parallel, receding supporting plates, without a cardinal
process, adductor muscle scars hexagonal in outline, expanding anteriorly from the
anterior ends of the supporting plates.
TYPE SPECIES. Rectotrophia globularis sp. nov. from the Treiorwerth Formation.
DISCUSSION. The Heunellidae, into which the new genus falls, at present com-
prises two subfamilies, the Huenellinae, without a cardinal process, and the Meso-
nomiinae, with a rudimentary cardinal process and recumbent brachiophore plates.
Both families are also characterized by the development of a fold and sulcus, and
by having non-parallel supporting plates. The disposition of the supporting plates
in the new genus, together with the shape of the valves and the absence of fold or
sulcus, necessitate the erection of a new sub-family.
Rectotrophia globularis gen. et sp. nov.
(PI. 10, figs. 11-17)
DIAGNOSIS. As for genus.
AND TRILOBITES OF ANGLESEY
177
TYPE SPECIMENS (measurements in mm.)
Length
6-7
Width
7-0
6-7 (est.)
5'7
HOLOTYPE. Internal mould of pedicle valve (Af.i436)
PARATYPES. Internal mould of brachial valve (Af . 1436)
Internal mould of brachial valve (Af . 1442) 6 • 7
TYPE HORIZON AND LOCALITY. Treiorwerth Formation, sandstones 300 yds.
south-east of Ffynnon-y-mab, Trefor. N.G.R. 36247950.
DISCUSSION. The genus is known only from a few internal moulds, from Greenly's
collection, the writer having found no well-preserved specimens. As a result no
mean estimates of proportions can be included in a precise specific diagnosis. The
holotype is 2-8 mm. thick, and the dental lamellae are 1-7 mm. apart. In the
first paratype (Af.i436) the supporting plates are 1-9 mm. apart, in the second
they are 1-5 mm. apart and the adductor muscle scars are 1-9 mm. long.
Family PORAMBONITIDAE Davidson 1853
Genus PORAMBONITES Pander 1830
Porambonites (s.s.) sp.
(PI. n, figs. 1-6, 8)
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal and external moulds of pedicle valve
(BB.30598a-b) 18.0
Internal and external moulds of brachial valve
(BB.30599a-b) 20-5 23-2
Internal mould of brachial valve (BB . 30600) . 13 -3 12-5
HORIZON AND LOCALITY. Treiorwerth Formation, sandstones 300 yds. south-
east of Ffynnon-y-mab, Trefor. N.G.R. 36247950.
DISCUSSION. The specimens are all disarticulated, incomplete, and have suffered
some distortion. Since the species of Porambonites are to a large extent based on
external form it is not possible to make a close comparison with any described
species. In addition the fold and sulcus do not develop until the shell is well grown,
and of the figured specimens only BB . 30599 has a good fold.
The valves are roughly circular in shape, and so do not belong to the subgenus
Equirostra (Isorhynchus). The pedicle valve is lenticular, without a swollen umbo,
the brachial valve more convex. The internal features of both valves are well
preserved, but only the dorsal muscle scars are visible. The adductor scars are
bluntly wedge-shaped and form an arc lying anterior to the ends of the supporting
plates. The diductor scars are four(?) in number forming a narrower central pair
flanked by two wider scars.
Allied species, from the lower Ordovician of the Baltic are P. broggeri Lamansky,
P. altus Pander and P. planus Pander,
178 LOWER PALAEOZOIC BRACHIOPODS
Family CAMERELLIDAE Hall & Clarke 1894
Subfamily CAMERELLINAE Hall & Clarke 1894
Genus CAMERELLA Billings 1859
Camerella sp.
(PL n, figs. 7, 9-11)
FIGURED SPECIMEN. Complete shell (66.30597), length 4-8 mm., width 5-1
mm., thickness 2-9 mm.
HORIZON AND LOCALITY. Garn Formation, limestone blocks in breccia beds,
Forth Padrig, Mynachdy. N.G.R. 30539279.
DISCUSSION. The figured specimen is the only complete one known, the others
being only fragments of smaller valves. It is sub-triangular, slightly wider than
long, with both valves approximately equally convex. The dorsal fold at the
anterior margin is two-thirds the width of the valve, and originates at 2-6 mm.
anterior to the umbo. It comprises two bounding costae, separated by a shallow
depression which corresponds to a low costa or fold in the pedicle valve. The
ventral sulcus is flanked by a pair of subangular costae. A few growth lines on
the pedicle valve show the outline to have been sub-circular until the fold and sulcus
started to develop.
The majority of described species of Camerella have three or more costae developed
on the fold, all the costae appearing at the same time, that is, when the fold starts
to appear. C. unicostata (Cooper 1956 : 583, pi. 113, B, figs. 6-9) has a similar
development of costae on the fold and sulcus, but has more costae on the flanks,
and, at the same size, seems to be more tumid and is suboval in outline.
Suborder PENTAMERIDINA Schuchert & Cooper 1931
Superfamily PENTAMERACEA M'Coy 1844
Family PARALLELELASMATIDAE Cooper 1956
Genus METACAMERELLA Reed 1917
Metacamerella cf. balcletchiensis (Davidson)
(PL n, figs. 12-14)
1919 Camarella? [cf. Stricklandinia? balcletchiensis (Dav.)] ; Matley in Greenly : 478.
FIGURED SPECIMEN. Complete shell (Af.isgo) length 21-1 mm., width 20-0
mm., thickness 15-0 mm.
HORIZON AND LOCALITY. Garn Formation, limestone blocks in breccia beds,
Forth Padrig, Mynachdy. N.G.R. 30539279.
DISCUSSION. The only specimen so far found, a complete shell from Greenly's
collection, is very similar to the Girvan species (Williams 1962 : 232). The outline
is comparable, with 'false interareas' extending just over half the length of the
shell, and, so far as can be seen, a very low fold on the antero-median part of the
brachial valve, The ornament is also very similar, consisting of about six low rounded
AND TRILOBITES OF ANGLESEY 179
costae, with a wavelength of 2 mm. at 13 mm. from the umbo. The interior details
are not seen and hence cannot be compared with M. balcletchiensis.
Order uncertain
(PI. 10, figs. 18-24)
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal and external moulds of pedicle valve
(BB . 55792a-b) 18-9 18-6
Internal and external moulds of brachial valve
(BB.5579ia-b) . 20-5
HORIZON AND LOCALITY. Torllwyn Formation, sandstone 50 ft. above the base
of the succession on the north side of the faulted syncline, 45 yds. north of Ogof
Gynfor, Llanbadrig. N.G.R. 37859490.
DISCUSSION. The valves are rostrate and convex, roughly circular in outline.
The pedicle valve bears a strongly marked sulcus with a flattish floor, flanked by
angular folds, and has a narrow curved interarea. The delthyrium is apparently
open. The brachial valve bears a corresponding fold, and both valves are costellate,
with flat-topped costellae interspersed with narrow interspaces. In the ventral
interior the dental lamellae are almost parallel, the muscle scars raised on a wad
of callus extending anterior to the lamellae on a pseudospondylium which is rounded
at its anterior end. The dorsal cardinalia are not fully preserved, though supporting
plates diverge to the floor of the valve.
The external shape and ornament of the valves suggests the syntrophiid Rhyso-
strophia, but the internal structures differ considerably, and the specimens may
well belong in the Orthida.
V. SYSTEMATIC DESCRIPTION OF THE TRILOBITA
Family ASAPHIDAE Burmeister 1843
Subfamily OGYGIOCARIDINAE Raymond 1937
Genus OGYGIOCARIS Angelin 1854
Ogygiocaris selwynii (Salter)
(PI. 12, figs. 1-2, 5-6)
1919 Ogygia selwyni Salter; Lake in Greenly : 442, 446.
DESCRIPTION. Cranidium quadrilateral, wider than long, evenly convex (tr.).
Glabella almost as long as cranidium, sides almost parallel but slightly constricted
opposite the eyes, anterior margin semicircular; evenly convex (tr.), slightly con-
vex (longit.) with a dome-shaped anterior lobe; glabellar furrows almost obsolete;
one pair faintly impressed midway along the glabella. Axial furrows weak, ending
in shallow hypostomal pits; occipital ring reduced to a pair of triangular raised
portions pointing inwards to the tubercle, with a narrow articulating ring formed
by a faint furrow behind the triangular facets (following Harrington & Leanza's
interpretation, 1957 : 177). Preglabellar field absent. Fixigenae triangular shaped
r8o LOWER PALAEOZOIC BRACHIOPODS
areas behind the eyes. Posterior border sloping slightly backwards; posterior
border furrow broad and shallow, opposite the occipital ring adaxially. Eyes
semicircular, very close to and centred on the transverse midline of the glabella.
Facial suture isoteliform, with the anterior branches widely divergent in front of
the eyes, meeting in an even curve without any apparent acumination; posterior
branches oblique backwards and outwards, sigmoidal.
Pygidium transverse, one and one-half times as wide as long; anterior margin
convex forwards, postero-lateral margins convex, with the greatest curvature
across the midline. Axis tapering backwards, not extending onto the posterior
border and with the end rounded; probably with eight or more axial rings; narrow
(longit.) articulating half ring. Marked anterior border. Pleural fields with pleural
furrows marking more than four segments, each bearing oblique ridges near their
outer ends. Border of uniform width, one-fifth the length of the whole pygidium,
concave but with a convex ridge against the pleural fields. Doublure convex
ventrally and of the same width as the border.
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal mould of cranidium (Af . 842) . . . distorted
Internal mould of cranidium (Af. 823) . . . 31-5 36-0
Internal mould of pygidium (Af . 820) . . . 37*5 54-0 (est.)
Internal mould of pygidium (Af . 821)
HORIZON AND LOCALITY. Carmel Formation, sandstones. Af .820-823 from the
scarp west of Bryn Gollen Uchaf (Bryn Gwallen of Greenly), N.G.R. 40558380;
Af.842 from quarry 400 yds. north-north-west of Bryn Gollen Uchaf, N.G.R.
40508425.
DISCUSSION. The cranidia correspond closely with that of 0. selwynii as des-
cribed by Whittard (1964 : 233) though it is difficult to recognize the glabellar
furrows. In particular the anterior portions of the facial sutures diverge at the
same angle, and their course close to the median suture is also similar.
Af .820, the internal mould of the pygidium differs in that the posterior border
is more strongly curved across the midline than laterally, whereas the reverse is
true of 0. selwynii (Whittard 1964 : 235). Af.82i shows oblique ridges in
addition to the pleural furrows.
Family THYSANOPELTIDAE Hawle & Corda 1847
Genus PROTOBRONTEUS Snajdr 1960
Protobronteus greenlyi sp. nov.
(PI. 12, figs. 3-4, 7)
1919 Illaenus caecus Holm (partim) ; Lake in Greenly : 478.
DIAGNOSIS. A species of Protobronteus with no inner anterior border furrow,
and an ornament of coarse terrace lines without intervening pits, transverse in
alignment over the anterior part of the fixigenae.
DESCRIPTION. Both cranidia incomplete, probably semicircular with truncated
AND TRILOBITES OF ANGLESEY 181
corners. Glabella clavate, reaching to the anterior border, evenly convex (sag.
and tr.); narrowest just behind the midline (sag.), just longer than wide; without
glabellar furrows. Axial furrows convex inwards, well defined. Occipital ring
not seen. Fixigenae incomplete, evenly convex (long.), palpebral lobe and course
of facial suture not seen. Anterior border not separated from glabella mesially,
but present in front of the nxigenae; anterior border furrow well defined, meeting
the axial furrow in a right angle, and continuing a little way adaxially to define the
anterolateral corner of the glabella. Ornament of coarse terrace lines, averaging
five to eight per 5 mm., becoming crowded together on the anterior border, trans-
verse across the glabella, borders and anterior part of the fixigenae, not preserved
elsewhere.
Librigena incomplete, triangular, convex (long.), with prominent anterolateral
border furrow, no posterior border furrows. Eye lobe large, semicircular. Genal
spine long, circular in cross-section. Ornament of distant terrace lines, diverging
on either side of eye.
TYPE SPECIMENS (measurements in mm.)
Length Width
HOLOTYPE. Incomplete cranidium (In. 58291) . . 28-8
PARATYPES. Incomplete cranidium (In . 58292) .
Internal mould and interior of incomplete
librigena (In . 58293a-b)
TYPE HORIZON AND LOCALITY. Garn Formation, limestone blocks in breccia
beds, Forth Padrig, Mynachdy. N.G.R. 30539279.
DISCUSSION. Protobronteus was erected by Snajdr (1960 : 245-246) to include
only Eobronteus reedi Sinclair (1949 : 51-52). In this species, as in P. greenlyi
the glabella is clavate, without any glabellar furrows, and coalesces with the anterior
border. E. curtus Sinclair (1949 : 50-51) is very similar and could well be included
in Protobronteus as the glabellar furrows are indistinct and the anterior border
furrow fades out mesially.
P. greenlyi differs from both these species in that the inner anterior border furrow
is absent (the cheek furrow of Sinclair 1949 : 51), and the ornament is differently
developed. In P. reedi the terrace lines are longitudinal between the two border
furrows, and in E. curtus they are not developed in the same place, only coarse
punctae being present.
Family ILLAENIDAE Hawle & Corda 1847
Subfamily ILLAENINAE Hawle & Corda 1847
Genus ILLAENUS Dalman 1827
Illaenus sp.
(PL 12, figs. 8-13, 15)
1919 Illaenus caecns Holm (partim); Lake in Greenly : 478.
DESCRIPTION. Cranidium quadrangular, evenly convex (tr.), longitudinal con-
vexity strong posteriorly, weak anteriorly. Glabella short and wide, with slight
182 LOWER PALAEOZOIC BRACHIOPODS
independent convexity (tr.), two-thirds the width of the cranidium. Axial furrows
curve inwards for two-thirds of their length, and end in an outwards curve. Pal-
pebral lobes one-third the length of the cranidium, situated less than their own
length from the posterior margin. Posterior branches of the facial sutures short,
running directly backwards, anterior branches slightly divergent. Dorsal surface
of cranidium smooth.
Pygidium parabolic, the anterior margin slightly convex forwards, width four-
thirds the length, convex, the inner pleural fields gently convex and the margins
deflected at about 45°. Axis short, sub-triangular, with independent convexity
(tr.), four-tenths the width of the pygidium. Axial furrows shallow posteriorly,
meeting at about 60°. Short (long.) articulating half ring. Pleural fields with
anterior borders slightly swollen, marked off by shallow depressions. Articulating
facets sharply bevelled, with terrace lines extending beyond them. Rest of dorsal
surface finely pitted. Doublure close to the dorsal shield, convex ventrally at its
outer margin, almost half the length (sag.) and one-tenth the width of pygidium at
anterior margin. Inner margin commencing near midline of facet (tr.), swinging
in a curve gradually decreasing in radius to the midline of the pygidium, where a
forward pointing cusp is found. Ventrally deflected median ridge strongly marked.
Doublure bears terrace lines running parallel to its margins about 0-7 mm. apart.
FIGURED SPECIMENS (measurements in mm.)
Length Width
Cranidium (^.58294) ..... 9-9
Pygidium (In. 58295) 23-7 32-7
Pygidium (In. 58296) 22-6 33-5
DISCUSSION. The species resembles Illaenus revaliensis (Holm 1886 : 87-92,
pi. 2, figs, i-io) particularly in the shape and other features of the pygidium. The
axis is similar, and the inner margin of the doublure has a forward pointing cusp at
the midline. The cranidium is poorly preserved, and may possibly be a crushed
and distorted cranidium of Stenopareia cf. linnarssoni (Holm), but the glabella is
relatively wider, the palpebral lobes are much larger, and the anterior margin seems
to be sharply truncated.
Genus STENOPAREIA Holm 1886
Stenopareia cf. linnarssoni (Holm)
(PI. 12, figS. 14, 16-23)
1919 Illaenus caecus Holm (partim); Lake in Greenly : 478)
DESCRIPTION. Cranidium quadrangular, the frontal area domed, strongly and
evenly convex (long, and tr.). Glabella with slight independent convexity (tr.),
half the length of cranidium. Two pairs of oval muscle scars between the axial
furrows, the anterior pair indistinct. Axial furrows poorly defined on dorsal, but
well defined on ventral surface, extending forwards half the length of cranidium,
widening in their anterior half to be well defined on the ventral surface. Palpebral
lobes less than one fifth the length of cranidium, less than their own length from
AND TRILOBITES OF ANGLESEY 183
the posterior border. Posterior braches of facial suture short, straight, running
diagonally outwards, anterior branches straight, converging slightly forwards.
Glabella and fixigenae with smooth dorsal surfaces, frontal margin with faint terrace
lines on the ventral surface.
Librigena twice as long as wide, tapering to a point anteriorly, with vertically
deflected border present anteriorly. Genal angle very broadly rounded.
Rostral plate triangular, anterior margin gently convex outwards, the posterior
margins concave rearwards, meeting in a central cusp with an angle of less than 90°.
Ventral surface with terrace lines.
Pygidium semi-oval, just over half as long as wide, weakly convex except at the
sides where almost vertically deflected. Axis one-third the anterior width, un-
defined posteriorly, evenly convex (tr.). Axial furrows shallow, only seen at anterior
margin. Dorsal surface smooth. Articulating facets convex, almost vertical.
Doublure lies close to the dorsal surface, with a faint median ridge, anterior margin
monocuspid(P).
FIGURED SPECIMENS (measurements in mm.)
Length Width
Cranidium (In . 58297) 15-5 18 • 6
Cranidium (In. 58298) 14-6 (est.)
Librigena (^.58299) . . . . . . 19-7
Rostral plate (In . 58300) 8-9 22-6
Pygidium (In. 58301) 23-4 42-4 (est.)
Pygidium (In. 58302) . . . . 13-5 22-5
HORIZON AND LOCALITY. Garn Formation, limestone blocks in breccia beds,
Porth Padrig, Mynachdy. N.G.R. 30539279.
DISCUSSION. The cranidium is very similar to that of Stenopareia linnarssoni
(Illaenus linnarssoni Holm in Warburg 1925 : 115-123, pi. 2, figs. 14-18). The
glabellar proportions and the axial furrows are the same, with an anterior swelling
of the furrows. The palpebral lobes are the same size and equally far back. The
pygidia are approximately similar in proportion; the inner margin of the doublure
is unknown, though it also has a ventrally deflected median furrow. The facets
are narrow and rounded in both cases, but the axis is relatively narrower in the
Anglesey specimens. Stenopareia camladica Whittard (1961 : 216-217, pi. 30, figs.
10-13) nas a similar cranidium, but the axial furrows are poorly preserved, and the
pygidium is differently proportioned in the Shropshire species.
Family HARPIDAE Hawle & Corda 1847
Genus SELENOHARPES Whittington 1950
Selenoharpes (?) sp.
(PL 13, ngs. 1-2, 5-6)
DESCRIPTION. Outline of cephalon oval; greatest width probably behind the
occipital ring.
Glabella tapering forwards, width at its base seven-ninths of its length, rounded
1 84 LOWER PALAEOZOIC BRACHIOPODS
anteriorly; sharply convex and carinate, in height equal to its width; in lateral
profile becoming vertical anteriorly. Basal lobes triangular, very vague, one-third
the length of the glabella, marked by shallow furrows running inwards and back-
wards. Axial, preglabellar, and occipital furrows all shallow. Occipital ring one-
ninth length of the glabella, bent up with it.
Pre-glabellar field one-third length of the glabella, sloping anteriorly. Eye
tubercles prominent and elevated above the cheeks, opposite the anterior one-
fifth of the glabella. Eye ridges broad, running directly inwards. Genal ridges
fine, running outwards and backwards to the girder. Alae one-third the length
of the glabella, depressed, marked by semicircular alar furrows. Cheek lobes bent
down anterolaterally and laterally. Posterior border with sharply raised convex
rim, continuous with a similar rim on the inward side of the prolongations. Cheek
roll not separable from the cheeks. Brim equal in width anteriorly to the glabellar
length, convave, with a row of prominent pits just inside the rim marking the
inner edge of a downward bevel round the rim. Girder smooth, with prominent
pits forming a single row on both sides ; girder possibly meeting the internal prolonga-
tions. Glabella and alae smooth; preglabellar field and cheek lobes anterior and
lateral to the eyes with radiating ridges with fine pits between them; on the rest
of the cheeks and on the brim are similar fine pits but without ridges or arrangement.
FIGURED SPECIMEN. Incomplete cranidium (^.58303).
HORIZON AND LOCALITY. Garn Formation, limestone blocks in breccia beds,
Forth Padrig, Mynachdy. N.G.R. 30539279.
DISCUSSION. The two closest genera are Selenoharpes and Aristoharpes , the
former of Middle Ordovician (post-Llandeilo) age and the latter of Llandovery age.
In Selenoharpes the glabella tapers forwards, the eye ridges are prominent and genal
ridges are present. In Aristoharpes the glabella is sub-parallel sided, eye ridges
are weak and genal ridges absent. It also has much smaller alae than Selenoharpes,
which are one-quarter the length of the glabella compared with one-half. There is
thus some doubt as to where to place these specimens, which compare closely with
Selenoharpes, except for the smaller alae, a difference that is probably trivial. The
specimens are certainly not conspecific with the type species, S. youngi (Reed)
from the lower Caradoc of Girvan, in which the brim is convex upwards.
Family TRINUCLEIDAE Hawle & Corda 1847
Subfamily CRYPTOLITHINAE Angelin 1854
Genus BERGAMIA Whittard 1955
Bergamia (?) sp.
(PI. 13, figs. 3-4, 9> 13)
DESCRIPTION. Cephalon twice as broad as long. Glabella pyriform, swollen,
tapering markedly posteriorly, second and third furrows fairly well marked, pit-
like in form ; well marked alae bounded laterally by deep furrows, ending laterally
against the posterior border in well marked knobs ; glabellar furrows not well marked
AND TRILOBITES OF ANGLESEY 185
against the alae. Genae swollen, crossed by a ridge running obliquely back from
the front of the glabella to the genal angle. Occipital ring very narrow, arched
and convex posteriorly; posterior borders from a narrow sharp ridge posterior to
a wide shallow furrow. Glabella and genae posterior to the ridge bear a strong
reticulate pattern, becoming faint towards the front of the glabella. Fringe of
uniform width throughout except at the genal angle ; pits sunk in deep radial sulci ;
girder not seen in any of the specimens; sulci number eighteen on each side of the
centre-line, with up to four pits in each ; interradial sulci numbers i and ii present ;
some twin pits.
Thoracic segments not well preserved; axis strongly convex with axial rings
convex posteriorly; pleural regions with strong oblique pleural furrows; pleural
spines strong and directed posteriorly.
Pygidium over twice as wide as long, triangular in outline; axis tapers at 30°
with at least five axial rings, well defined and strongly arched; pleural lobes divided
by at least four faintly marked oblique interpleural furrows; anterolateral angles
bevelled as an articulating facet; posterior margins with a broad border of uniform
width, slightly raised over the centre-line.
FIGURED SPECIMENS. Counterpart moulds of cranidium and pygidium (In.
58304a-b). Length of cranidium (sag.) 3-4 mm., width 7-0 mm. Length of pygi-
dium i -7 mm., width 4-2 mm.
Counterpart moulds of complete dorsal carapace (In.58305a-b). Length (sag.)
2-5 mm.
Ventral mould of dorsal carapace (In. 58306) Distorted.
HORIZON AND LOCALITY. Shales, D. bifidus zone, quarry 100 yds. north of
Gwredog-uchaf farm, Rhodogeidio. N.G.R. 40488628.
DISCUSSION. The preservation of the specimens, in particular of the fringe, is
not good enough to make a certain generic identification. However, the simplicity
of the fringe suggests that the specimens belong to Bergamia, which ranges from
the uppermost Arenig through the Llanvirn, and possibly into the Caradoc (Whittard
I955 : 31)- The species resembles B. rhodesi Whittard (1955 : 32) in the arrange-
ment of the pits on the fringe. The smallest specimen illustrated (PI. 13, fig. 3)
is a meraspid of probably degree two. There is little difference in characters from
the larger specimens.
Family RAPHIOPHORIDAE Angelin 1854
Genus AMPYX Dalman 1827
Arnpyx sp. (i)
(PI. 13, %. 8)
1919 Ampyx cf. domains (Angelin); Lake in Greenly : 446.
1955 Ampyx sp.; Whittard : 17.
FIGURED SPECIMEN. Cranidium (Af .824). Length 9-0 mm., width 12-4 mm.
i86 LOWER PALAEOZOIC BRACHIOPODS
HORIZON AND LOCALITY. Carmel Formation, sandstones on the escarpment 300
yds. west of Bryn Gollen Uchaf. N.G.R. 40558380.
DISCUSSION. This specimen remains the only one collected from the basal grits,
and there is nothing that can be added to Whittard's opinion that it probably
belongs to an undescribed species.
Ampyx sp. (2)
(PL 13, figs. 7, 10-12)
1919 Ampyx nasutus Dalman; Lake in Greenly : 433.
DESCRIPTION. Cranidium quadrilateral in outline, length four-tenths the width,
the anterior border very well developed. Glabella pyriform, widest near the
anterior end and broadly rounded in front, one-third to one-quarter the width of
the cranidium in front, tapering to the occipital ring, exceptionally weakly swollen,
overhanging only part of the preglabellar field. One pair of glabellar furrows
almost isolating long narrow lobes, the furrows running back parallel to the axial
furrows, starting just anterior to the transverse midline of the glabella; alae (cf.
Whittard 1955 : 15) crescentic, starting anterior to the glabellar furrows and
extending backwards to meet the posterior border furrow, axial and alar furrows
faint; glabellar spine at least half as long as the cephalon, circular in cross section,
possibly concave dorsally. Fixigenae triangular, gently convex. Facial suture
runs in a gentle sigmoidal curve convex outwards as it crosses the posterior border,
convex inwards forwards of this and again convex outwards in its anterior third.
Occipital ring narrow, occipital furrow shallow, both convex backwards. Posterior
border furrow broad and shallow, running obliquely outwards and backwards,
but sweeping forwards again near the genal angle ; posterior border widening laterally.
Pre-glabellar field comparatively long, about one-sixth the length of the cephalon,
flattened.
Thorax of six segments, broad and flat. Axis convex, axial rings each with a
shallow groove defining small lobes at each side. Pleurae parallel-sided, each
with an oblique furrow curved forward at the tip, sharply deflected ventrally at
prominent fulcral processes which appear as tubercles. First or macro-pleurae
longer than the others with outer margins not deflected but sloping backwards and
out to the fulcrum. Other pleurae with blunt terminations.
Pygidium triangular, twice as wide as long. Anterior margin straight, postero-
lateral borders slightly convex, deflected, with terrace lines parallel to the margins.
Axis convex, with narrow articulating half-ring, tapering from one-fifth the width
of the pygidium anteriorly to a point at the posterior end, occasionally a few axial
rings present. Pleural lobes smooth, except for strongly developed anterior borders,
marked off by sharp furrows running obliquely backwards and outwards, becoming
concave forwards laterally to meet the anterolateral angle of the pygidium. Pro-
minent fulcral tubercle at the inner end of the articulating facet.
AND TRILOBITES OF ANGLESEY 187
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal and external moulds of cranidium (In.
58ao7a-b) 16-0 35«6(est.)
External mould of cranidium (In . 58308)
Internal mould of thoracic segments and pygidium
(Af.3653) . 16-3 19-3
External mould of pygidium (In . 58309) . . 7-0 16-8 (est.)
HORIZON AND LOCALITY. Tandinas shales, by the track leading down to the
quarry, and on the shore behind the power house, at Tandinas quarry, Careg-onen.
N.G.R. 58248187.
DISCUSSION. The species is similar to A. linleyensis Whittard of the Shelve area
(D. bifidus zone), but differs in having a short, weakly swollen glabella, a pre-glabellar
field, and having terrace lines on the pygidium. A. salteri Hicks (D. extensus
zone?) also has terrace lines to the pygidium, but lacks a pre-glabellar field.
Family CHEIRURIDAE Salter 1864
Subfamily CHEIRURINAE Salter 1864
Genus CERAURINELLA Cooper 1953
Ceraurinella sp.
(PI. 13, figs. 14-22)
DESCRIPTION. Cranidium roughly triangular in outline, broader than long.
Glabella evenly convex (tr.), gently convex (sag.) becoming more convex along
the anterior lobe. Length equal to the maximum width, the latter across the
anterior lobe, sides slightly tapering towards the occipital ring, front margin convex
forwards. Three pairs of narrow well marked glabellar furrows; ip inclined ob-
liquely backwards, bent back to join the occipital furrow nearer the midline than
the axial furrows; 2p and 3p parallel to each other, curving obliquely backwards
and crossing one-third the width of the glabella (tr.). Basal lobes with independent
convexity, one and a half times the length (exsag.) of the second and third lobes;
the latter subequal in length without independent convexity. Occipital furrow
not well seen, shallow. Fixigenae triangular convex, eye lobe on the highest part,
opposite and close to the second glabellar lobe, equal in length to that lobe (exsag.).
Anterior part of fixigenae parallel sided, anterior branch of facial suture running
in to meet the axial furrows just in front of 3p glabellar furrows. Posterior branch
of facial suture runs transversely out from the eye, and curves round to meet the
anterolateral border of the cranidium. Posterior border furrows deep and wide,
bending sharply forwards to meet the lateral border furrow. Posterior border
widening laterally towards genal spine, length of latter unknown. Glabella and
borders smooth, fixigenae coarsely tuberculate. Librigenae unknown.
Hypostome slightly longer (sag.) than maximum width (tr.) across anterior wings,
i88 LOWER PALAEOZOIC BRACHIOPODS
tapering backwards to a width at the posterior border half the maximum. Median
body convex (sag. and tr.) widest in front of anterior wings. Anterior, lateral and
posterior border furrows broad and shallow. Middle furrows faint, running in
from opposite shoulders to end in shallow pits. Posterior lobe crescentic, independ-
ently convex where marked off by the middle furrows. No anterior border medianly.
Anterior wing slopes steeply dorsoposteriorly, tip narrow and spine-like. Lateral
border commences opposite anterior wing, widens rapidly to prominent and sharp
shoulder (in ventral view) wh'ch is just less than half the way back (exsag.) from
the anterior border, continuous with the posterior border. Short denticle or spine
on the posterolateral corners, posterior border straight. Posterior wing not seen.
Entire surface smooth.
Thorax of unknown number of segments. Axis arched, most sharply convex
over the midline, length (sag.) one-fifth the width, width one-quarter that of the
whole segment. Anterior margin convex forwards over the midline, concave
forwards laterally above the apodemes, which are deflected ventrally (no articulating
half -ring seen). Inner part of pleura horizontal, divided in two by a furrow parallel
to the axial furrow, the inner part being one-third the width of the whole, and
crossed by a diagonal furrow, the outer part bent abruptly ventrally and forming
a gradually tapering pleural spine. No ornament on the segments.
Pygidium poorly preserved. Convex axis with four axial rings, or three axial
rings and an articulating half ring. Margin not preserved, except for one long
tapering spine probably commencing opposite the second axial ring and curving
backwards towards its tip. No ornament present.
FIGURED SPECIMENS (measurements in mm.)
Length Width
Incomplete glabella (In. 58310) .... 8-7
Incomplete glabella (In. 58311) .... 10-3
Incomplete cranidium (In. 58312) . . . 13-6
Hypostome (111.58313)
Hypostome (In. 58314) 7-9 5 '4
Hypostome (^.58315) 9.1
Thoracic segment (In. 58316) ....
Thoracic segment (In . 58317)
Incomplete pygidium (In. 58318) ....
HORIZON AND LOCALITY. Garn Formation, limestone blocks in breccia beds,
Porth Padrig, Mynachdy. N.G.R. 30539279.
DISCUSSION. The specimens are assigned to Ceraurinella since the eyes are
opposite the 2p lobes and near the glabella, the genal spines though not complete
are short, the pygidium has the long spines typical of that genus (and Ceraurus),
and the thoracic segments and hypostome also are of the same type. The species
described by Cooper (1953 : 29-30) and by Whittington & Evitt (1953 : 62-70)
differ in their ornament, which is more pervasive, and possibly also in other minor
details. None of the species of Ceraurus (Raymond & Barton 1913; Barton 1913)
AND TRILOBITES OF ANGLESEY 189
corresponds. Ceraurinella? sp. has been recorded by Whittington from the Derfel
limestone (in Whittington & Williams 1955 : 422-423, pi. 40, figs. 102, 107 and
in), but the two species are not the same, as in his figures the eyes, not preserved,
cannot have been farther back than opposite the 3p glabellar lobes, and the 3p lobes
seem to be longer (sag.) than the others.
Subfamily SPHAEREXOCHINAE Opik 1937
Genus SPHAEREXOCHUS Beyrich 1845
Sphaerexochus sp.
(PL 14, figs. 1-2)
DESCRIPTION. Cranidium only preserved, distorted by flattening, crescent shaped
in outline, original convexity not known. Glabella subcircular to pentagonal in
outline, widest opposite the second glabellar furrow (2p). Occipital ring narrower
than the glabella at its maximum, one-eighth of glabella length (sag.), convex,
posterior margin concave backwards. Occipital furrow broad and deep, uniformly
curved throughout. First glabellar furrows (ip) transverse with a gently concave
backwards curve, curving sharply at their inward ends towards the occipital furrow,
running to meet it in another gentle curve convex sagittally. The first lateral
glabellar lobes isolated, subquadrate in outline, possibly without independent con-
vexity, four-ninths the length of the glabella (sag.), approximately two-ninths its
width. Second glabellar furrow (preserved only on one side) very short, straight.
Second glabellar lobe one-half length of the first. No third glabellar lobes or furrows.
Anterior border not preserved. Fixigenae small, triangular, convex. Palpebral
lobe very narrow, opposite to ip furrow, two-thirds the length of the first lobes.
Facial suture not seen forward of the eye. Posterior branch runs outwards and
then backwards to meet the posterior border at right angles. Posterior border
equal in width to the occipital ring at its inner end, widening towards the genal
angle. Posterior border furrow concave forwards, dying out towards the genal
angle.
FIGURED SPECIMEN (measurements in mm.)
Length Width
Cranidium (^.58319) . . . . 6-0 (sag.) 9-5
HORIZON AND LOCALITY. Tandinas shales, on the shore by the powerhouse,
100 yds. west of the pier, Careg-onen. N.G.R. 58208193.
DISCUSSION. The specimen differs from all described species of Sphaerexochus
by having two pairs of lateral glabellar furrows. 5. bilobatus (Whittard 1958 : no)
has only the basal pair developed, otherwise three pairs seem to be the rule. The
preservation of the specimen has resulted in accentuation of the anterior furrow
on one side, and its obliteration on the other. It is possible, though unlikely that
a third pair of furrows may be present, but obliterated.
GEOL. 16, 4. 19
igo LOWER PALAEOZOIC BRACHIOPODS
Family PLIOMERIDAE Raymond 1913
Subfamily PLIOMERINAE Raymond 1913
Genus PLIOMEROPS Raymond 1905
Pliomerops sp.
(PI. 14, figs. 3-4, 6-7)
DESCRIPTION. Cranidium incomplete. Glabella quadrangular, expanding for-
wards from the occipital ring to midway between the pre-occipital and middle
furrows, forwards of this having a domed margin, slightly flattened in the centre.
Dorsal furrows deeply impressed. Pre-occipital furrows (ip) commencing at one-
third the length of the glabella forwards from the occipital ring, running obliquely
inwards and backwards for one-quarter the width of the glabella, at that point
turning abruptly to run slightly forwards, finally curving round to point obliquely
backwards at their inner tips, which are separated by one-eighth the width of the
glabella. Middle furrows (2p) commencing just forwards of two-thirds the length
of the glabella, running inwards and backwards to as near the midline as the pre-
occipital furrows, the tips of the inner ends of the two pairs of furrows being much
closer together than their outer ends. Anterior furrows (3p) located on the anterior
margin, half way between the midline and the anterolateral corner of the glabella,
faint and short, being little more than indentations of the margin. Rear two pairs
of glabellar lobes with independent convexity. Axial furrows of the same depth
as the glabellar furrows, curving smoothly into the anterior border furrow. Occipital
furrow convex forwards at centre, becoming concave forwards towards the axial
furrows. Occipital ring not completely preserved, lengthening (sag.) towards the
midline. Anterior border strongly arched dorsally over the midline, widest at the
midline and at the anterolateral angles of the cephalon. Fixigenae incompletely
preserved.
Hypostome shield-shaped, anterior border convex, lateral and posterior borders
with a sigmoidal curve ending in a posterior point, slightly wider than long, almost
flat. Middle body of same shape. Anterior lobe produced into lateral wings,
posterior lobe crescentic, defined by middle furrows commencing just behind the
wings, broad and shallow, curving gradually inwards. Anterior border poorly
preserved, widest at the anterior wings. Lateral and posterior borders of uniform
width except at their anterior ends. All border furrows wide and shallow.
Pygidium with shape of an extremely taut bow, just longer than wide, anterior
margin very convex forwards. Convex (tr.), the margins deflected ventrally at
angles up to 90°, almost flat (sag.), but convex (exsag.). Axis convex, of five flat-
topped (sag.) axial rings, tapering backwards, followed by a terminal axial piece
one and one half times as long as the rings, parallel sided for half its length and
tapering to a point in the posterior half. Pleural portions of five pleural lobes,
without a border, each lobe widening to the margin and truncated to produce a
smooth lateral and posterior border ; the last pair surrounding the axis and separated
by a median furrow.
AND TRILOBITES OF ANGLESEY 191
FIGURED SPECIMENS (measurements in mm.)
Length Width
Incomplete cranidium (In. 58320) . . . 16-5
Hypostome (In. 58321) 14-5
Pygidium (^.58322) 39-0
Internal mould and interior of pygidium (In.
58323a-b) . 17-0 (est.)
HORIZON AND LOCALITY. Garn Formation, limestone blocks in breccia beds,
Forth Padrig, Mynachdy. N.G.R. 30539279.
DISCUSSION. The above descriptions are of isolated pieces from the limestone
blocks, and, assuming they belong together, they are assigned to the genus Pliomerops
Raymond on the basis of the diagnosis given by Harrington (in Moore 1959 : 0 440).
The anterior border is not denticulate, there is no median indentation of the glabella,
and the terminal axial piece is long and enclosed. The cranidium resembles that
of P. canadensis (Billings) illustrated in the Treatise (Moore 1959 : fig. 345, 2b)
but the pygidia do not. As far as can be seen, most of the described species of
Pliomerops have short terminal axial pieces and usually a denticulate margin,
though the diagnosis in the Treatise (Moore 1959 : 0 440) states that the terminal
axial piece is long. Reed (1906 : 153, Plate XIX, fig. 16) figures a pygidium very
like this as Pliomera sp.
B. N. Cooper (1953) has described a pliomerid from Virginia, Pliomerella ameri-
cana, which is somewhat similar to the Anglesey specimens. The pygidium appears
to be identical, to judge from PL 10, fig. 4 of his paper. This is a crushed specimen,
but the long axial piece is apparently enveloped by the posterior pleurae. Another
pygidium is illustrated in fig. I of the same plate, in which the terminal axial piece
is quadrate and reaches the posterior margin, though it may be that the posterior
part is missing, and the caption states that the specimen is incomplete. Cooper's
text does not indicate whether the axial piece is enveloped or not, and the specimen
of his PI. 10, fig. i is re-illustrated on p. 0 445 of the Treatise (Moore 1959 : fig.
348, 2b) as being in fact complete. The accompanying text in the Treatise (Moore
1959 : 0445) states that a pygidium of this sort is diagnostic of Pliomerella. The
genus was erected by Reed (1941 : 269) for trilobites with two pairs of glabellar
furrows 'combined with some characters of Pliomera' ' , but he did not describe a
pygidium. It is thus probable that Pliomerella americana Cooper does not belong
to Pliomerella, but possibly to Pliomerops, though there is no sign in Cooper's figures
of the anterior glabellar furrows, nor does he describe them in the text.
Subfamily PLACOPARIINAE Hupe 1953
Genus PLACOPARIA Hawle & Corda 1847
Placoparia sp.
(PI. 14, fig. 5)
1919 Placoparia sp. : Lake in Greenly : 466.
FIGURED SPECIMEN. Dorsal carapace (Af.i3i9). Length 23-1 mm.
GEOL. 16, 4. !Q§
I92 LOWER PALAEOZOIC BRACHIOPODS
HORIZON AND LOCALITY. Shales of the Gl. teretiusculus zone, 80 yds. north of
the streamlet, on the shore at Porth-y-gwichiaid (Greenly 1919 : 466). N.G.R.
48799160.
DISCUSSION. The species P. zippei (Boeck) has recently been divided into two
species, P. zippei and P. barrandei Prantl & Snajdr, differing in a number of small
features, including the glabellar shape, details of the glabellar and occular furrows,
and the development of vincular notches (Whittard 1966 : 283-284). P. barrandei
itself is a synonym of P. cambriensis Hicks (1875 : 186, pi. 9, figs. 1-2) (Dr. W. T.
Dean, personal communication).
The Anglesey specimen belongs more probably to P. cambriensis, as the glabella
is quadrate rather than trapezoidal in outline, though the evidence of the other
features is equivocal, probably due to crushing of the specimen.
Family CALYMENIDAE Burmeister 1843
Subfamily CALYMENINAE Burmeister 1843
Calymenid undet.
(PI. 14, figs. 8-9, 12-13)
FIGURED SPECIMENS (measurements in mm.)
Length Width
Hypostome (^.58324) 6-7 5-6
Pygidium (In. 58325) . 9-3 H'5
HORIZON AND LOCALITY. Garn Formation, limestone blocks in breccia bed,
Porth Padrig, Mynachdy. N.G.R. 30539279.
DISCUSSION. The material found consists of one complete pygidium, and one
complete and one incomplete hypostome. It is assumed that they all belong to
one species.
The pygidium is oval in outline, and strongly convex. The axis gradually tapers
backwards, not reaching the posterior border, with six well defined axial rings,
a terminal piece and an articulating half ring. The pleural portions show deep
pleural furrows with much shallower interpleural furrows, extending to the margin
but becoming much fainter on the border. The border is marked by faint depres-
sions running from the tip of the axis to the anterior margins. There are well
defined and almost vertically deflected articulating facets, with the foremost pleural
groove extending onto them. In posterior view the lateral and posterior margins
show a strongly marked arch across the midline. The entire surface, except for
the articulating facets and the furrows, is finely tuberculate.
The hypostome is longer than wide, rectangular in outline. The middle body
is parallel-sided, with faint diagonal middle furrows dividing off a crescentic posterior
lobe, convex longitudinally and sharply convex transversely, without a raised
central portion to the anterior lobe. The anterior border is flexed ventrally, con-
tinuous with large anterior wings. The lateral borders have a wide gently curved
notch extending from the anterior wings to opposite the anterior end of the posterior
lobe. The lateral and posterior borders behind this are wide and flat, produced
AND TRILOBITES OF ANGLESEY 193
into points almost one-third of the length of the hypostome, separated by a deep
median notch extending to the end of the middle body. The tips of the points
and the notch are all sharp, each with an angle of about 50°.
Subdivision of the Calymeninae is based mainly on cephalic characters, so it is
not possible to give a generic designation. The upper Ordovician calymenid species
have been assigned to five different genera by Shirley (1936 : 400), and of these
Platycalymene , Gravicalymene and Flexicalymene agree in their pygidal characters.
Flexicalymene is the closest in character, and the pygidium described and figured
by Shirley (1936 : 406, pi. 29, fig. 7) looks similar, though it is more angular in
outline.
Family HOMALONOTIDAE Chapman 1890
Subfamily EOHOMALONOTINAE Hupe 1953
Genus NESEURETUS Hicks 1872
Neseuretus monensis (Shirley)
(PI. 14, figs, n, 16)
1919 Calymene parvifrons Salter; Lake in Greenly : 442, 446.
1919 Calymene tristani Brongniart; Lake in Greenly : 442.
1936 Synhomalonotus monensis Shirley : 401.
FIGURED SPECIMENS (measurements in mm.)
Length Width
Internal and external moulds of pygidium (In.
58326a-b) 16-9 21-0 (est.)
Internal mould of pygidium (In . 58327) . . distorted
HORIZON AND LOCALITY. Carmel Formation, sandstones ; In . 58326a-b from 440
yds. north of Ty-hen, Treiorwerth, N.G.R. 35767891; In. 58327 from 120 yds.
north-west of Chwaen-bach, Llanerchymedd, N.G.R. 39468378.
DISCUSSION. Shirley described this species from specimens in Greenly's collection
(G.S.M. Af. 930-2). The thorax, librigenae and pygidium were not represented
in the collection, so only the cranidium was described. Pygidia have been found
from the same horizon, and give additional information on the species. The speci-
men from Chwaen-bach is distorted, and the description is based on that from
near Ty-hen (^.58326).
The pygidium is broader than long, roughly elliptical but with the anterior margin
more strongly curved than the borders. The axis bears an articulating half ring
and furrow. The axis is funnel-shaped, the tapering portion containing at least
six rings, followed by an almost cylindrical portion terminating in a rounded end
not quite reaching the posterior margin. The pleural lobes are gently convex, and
bear six rounded unfurrowed pleurae, separated by well marked interpleural furrows.
The border is sharply rounded, but the form of the doublure is unknown. The
pygidium from Chwaen-bach shows pleural furrows which may be the result of
crushing.
194 LOWER PALAEOZOIC BRACHIOPODS
Family LICHIDAE Hawle & Corda 1847
Subfamily TETRALIGHINAE Phleger 1936
Genus AMPHILICHAS Raymond 1905
Amphilichas sp. (i)
(PL 14, figs. 10, 14-15, 17)
DESCRIPTION. Cranidium roughly pentagonal, strongly bent down at the an-
terior and posterior lateral corners. Glabella rounded, axe-shaped, as broad as
long, strongly convex, overhanging in front. Frontero-median lobe prominent,
expanded in front to more than twice its basal width; anteriorly strongly convex;
anterior lateral angles rounded; posteriorly parallel sided and less convex. First
lateral (longitudinal) furrows run inwards towards centre of lobe, curving steadily
round to become parallel and meet the occipital furrow at right angles. Lateral
lobes gently convex, a little less elevated than the median lobe; bluntly pointed
in front, strongly bent down with the antero-median lobe; posterolateral angles
extend considerably further back than the median lobe. Axial furrows as strong
as longitudinal furrows, posteriorly parallel to them, diverging slightly in front of
the eyes. Occipital furrow straight and horizontal behind median lobe, directed
obliquely backwards behind the lateral lobes, and less obliquely behind the fixigenae.
Occipital ring not completely preserved but possibly widest behind the median
lobe. Fixigenae posteriorly equal in width to the lateral lobes, narrowing to less
than half that width opposite the eye; expanding in front of the eye; expanding
in front of the eye but not completely preserved. Course of facial suture only
seen round eye, running outwards behind it. Palpebral lobe semicircular, convex
inwards; its length is one-fifth that of the glabella and its posterior end level with
the occipital furrow. Entire cranidium, except for the furrows, covered with
tubercles of varying size, irregularly placed.
Hypostome oval in outline, broader than long. Posterior border broad, posterior
margin indented. Middle body circumscribed. Posterior lateral lobes well defined
by median furrows running inwards slightly posteriorly with short bifurcations
at their inner ends. Lateral borders broad, with short triangular wings opposite
the posterior border furrow. Anterior border appears to be lacking. Anterior
part of middle body pitted; anastomosing ridges or terrace lines on remainder of
surface.
FIGURED SPECIMENS (measurements in mm.)
Length Width
Incomplete cranidium (In . 58328) . . . 14-9
Hypostome (In. 58329) .... 5 -8 (sag.) 7-9
HORIZON AND LOCALITY. Garn Formation, limestone blocks in breccia beds,
Porth Padrig, Mynachdy. N.G.R. 30539279.
DISCUSSION. No thoracic segments have been found, and the only remains of
pygidia so far found are too incomplete to describe; they only show the typical
development of tubercles, The cranidium shows similarities to A, wahlenbergi
AND TRILOBITES OF ANGLESEY 195
Warburg from the Leptaena Limestone in Dalarne, and also to Lichas (Amphilichas)
hibernicus (Portlock) (Reed 1906 : 106, pi. 15, fi. I non 2-3).
Amphilichas sp. (2)
(PI. 14, figs. 18-19)
DESCRIPTION. Outline possibly semicircular, weakly convex both longitudinally
and transversely, probably crushed. Frontero-median lobe convex, expanding
forwards to over twice its posterior width; the longitudinal furrows being parallel
posteriorly and curving outwards to diverge at more than 90° where they meet the
axial furrow, not reaching the occipital furrow but ending in a pit. Tri composite
lobe widening very slightly forwards, at its posterior end the same width as the
median lobe posteriorly; axial furrows concentric with the longitudinal furrows
but with smaller radius of curvature. Fixigena incomplete, narrow, posterior to
the eye less than half the width of the tricomposite lobe, cut into by the eye lobe,
which is one-fifth the length of the cranidium. Only a fragment of the occipital
ring preserved. Surface evenly pitted.
FIGURED SPECIMEN (measurements in mm.)
Length Width
Incomplete external mould of cranidium (Af.
3000) 17 app.
HORIZON AND LOCALITY. Tandinas shales, by the track 50 yds. west of Tandinas
quarry, Careg-onen. N.G.R. 58248187.
DISCUSSION. There appear to be no basal lobes, so that the specimen belongs
to Amphilichas, although there is little to compare closely with Amphilichas sp. (i)
from Forth Padrig.
Family uncertain
Genus MONELLA nov.
DIAGNOSIS. Genus similar to Glossopleura Poulsen, but differing in having more
strongly marked glabellar furrows, the anterior ends of the palpebral lobes not
touching the glabella, and eleven (compared with eight) thoracic segments.
TYPE SPECIES. Monella perplexa sp. nov. from the Carmel Formation.
DISCUSSION. The specimens assigned to the new genus were referred by Lake
(in Greenly 1919) to Ogygia, but certainly do not belong to the suborder Asaphina.
The thorax consists of eleven segments and the glabella is distinctly furrowed,
a combination of characters that is quite different from any contemporary trilobites,
but generally characteristic of the Order Corynexochida, though the rostral plate
and hypostome have yet to be found. The glabella is clavate and reaches the
anterior margin, the eyes are large and semicircular, with prominent palpebral
lobes, though eye ridges are not present. The closest genera are found in the family
Dolichometopidae, of the order Corynexochida. Athabaskiella has a similar cephalon,
but a smaller pygidium with only four segments differentiated in the pleural regions
ig6 LOWER PALAEOZOIC BRACHIOPODS
and fewer in the axis. Bathyuriscus has smaller eyes which are not semicircular,
and a very narrow border to the pygidium. Dolichometopsis has a pygidium without
a border and with a terminal indentation, and Glossopleura has very faint glabellar
furrows, only eight thoracic segments, and differs in the position of the palpebral
lobes.
Monella perplexa gen. et sp. nov.
(PL ii, figs. 15-21)
1919 Ogygia sp. (pars) ; Lake in Greenly : 446.
DIAGNOSIS. As for genus.
DESCRIPTION. Outline ovate, cephalon larger than pygidium. Cephalon semi-
circular, over twice as broad as long. Glabella clavate, between one and one-
quarter and two times as long as broad, convex transversely and slightly convex
longitudinally; glabellar lobes with independent convexity; three pairs of glabellar
furrows, one quarter the width of the glabella, shallow at their abaxial ends ; posterior
pair (ip) at one quarter the length of the glabella forwards, inclined obliquely
backwards and becoming shallower and wider at their adaxial ends; 2p inclined
slightly backwards, situated just forward of half the length of the glabella; 3p
transverse or slightly inclined forwards, nearer 2p than the front of the glabella;
anterior margin of glabella convex forwards, lateral margins and the distinct axial
furrows evenly and gently convex adaxially, with well marked fossulae midway
between 3p and the front of the glabella. Occipital ring continues the convexity
of the glabella, one sixth its length (sag.) ; occipital furrow distinct. Fixigenae
smaller than the glabella or the librigenae. Palpebral lobes semicircular, posterior
extremities just anterior to the base of the glabella; anterior extremities between
the 2p and 3p furrows, separated from the axial furrows at each end by one-third
the width of the glabella. No preglabellar field. Anterior border furrow narrow,
anterior border with a vertically deflected margin. Facial sutures opisthoparian,
posterior branches diverging backwards to cut the posterior margin midway between
the axial furrow and the genal spine; anterior branches run directly forwards from
the eye to the margin. Librigenae convex, genal spine equal in length to the
glabella. Posterior border straight to the facial suture, then curving abaxially
from it evenly round to the genal spine; posterior and lateral furrows well defined,
posterior border half the width of the occipital ring (sag.) ; the lateral border with
a vertical deflection. Doublure wide.
Hypostome and rostral plate unknown.
Thorax of eleven segments. Axis cylindrical, tapering slightly, equal
in width to the pleural regions, articulating half-rings equal in length (sag.) to the
axial rings; interpleural furrows curving slightly forwards towards the axial furrows.
Pleural regions flat adaxially, deflected ventrally in their abaxial regions; pleural
furrows transverse, dying out between fulcra and extremities; short, backwardly
directed pleural spines formed by the extremities of the pleurae being tapered.
AND TRILOBITES OF ANGLESEY 197
Anterior three(?) segments narrower (tr.) than the rest and undeflected at their ends.
Pygidium semicircular. Axis convex, tapering to a point and extending onto
the border but not reaching the posterior margin, eight or possibly more axial rings
present. Pleural lobes gently convex with pleural furrows only. Border broad,
concave, doublure equal to it in width.
TYPE SPECIMENS (measurements in mm.)
Length Width
HOLOTYPE. Counterpart moulds of complete dorsal
carapace (Af. 827-8) .... 13-7
PARATYPES. Internal mould of cranidium (Af .834)
Internal mould of cranidium (Af . 836)
Internal mould of pygidium (Af . 839)
OTHER FIGURED SPECIMEN
External mould of incomplete dorsal cara-
pace (In. 58290) ....
TYPE HORIZON AND LOCALITY. Carmel Formation, sandstones in old quarry
(now filled in), 400 yds. north-north-west of Bryn Gollen Uchaf, Llanerchymedd.
N.G.R. 40508425. Other figured specimen from same horizon, on the escarpment
50 yds. north-east of Prys-o wain-bach, Carmel. N.G.R. 38878283.
DISCUSSION. The generic position of M. perplexa has already been discussed,
and it is at present the only species known of the genus.
VI. REFERENCES.
ALIKHOVA, T. N. 1953. Rukovodyashchaya fauna brakhiopod Ordovitskikh otlozheniy severo-
zapadnoi chasti Russkoi Platformy. Vses. Nauchno-Issledov. Geol. Inst. (VSEGEI),
Minist. Geol. i Okhrany Nedr., SSSR, Trudy, 162 pp., 17 pi.
BANCROFT, B. B. 1945. The brachiopod zonal indices of the stages Costonian to Onnian
in Britain. J . Paleont., Tulsa, 19 : 181-252, pis. 22-38.
BARTON, D. C. 1913. A new genus of the Cheiruridae, with descriptions of some new species.
Bull. Mus. Comp. Zool. Harvard, Cambridge, Mass., 54 : 547-556, pi. i.
BATES, D. E. B. 1963. A lower Ordovician gastropod from Anglesey. Geol. Mag., Lond.,
100 : 258-259, pi. 17, figs. 10-12.
COOPER, B. N. 1953. Trilobites from the lower Champlainian Formations of the Appalachian
Valley. Geol. Soc. Amer., New York, Mem. 55 : 69 pp., 19 pis.
COOPER, G. A. 1956. Chazyan and related brachiopods. Smithson. misc. Coll., Washington,
127 : 1-1245, pi. 1-269.
DAVIDSON, T. 1866-1871. British Silurian Brachiopoda, 3. Palaeontogr. Soc. [Monogr.],
London : 1-397, pis. 1-50.
— 1868. On the earliest forms of Brachiopoda hitherto discovered in the British Palaeozoic
rocks. Geol. Mag., Lond., 5 : 303-316.
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London : 1-242, pis. 1-17.
GREENLY, E. 1919. The Geology of Anglesey. Mem. Geol. Sitrv. G.B. 980 pp., 74 pis.
HAWKINS, T. R. W. 1966. Boreholes at Parys Mountain, near Amlwch, Anglesey. Bull.
Geol. Surv. G.B., 24 : 7-18, pis. 2-3.
I98 LOWER PALAEOZOIC BRACHIOPODS
HESSLAND, I. 1949. Investigation of the lower Ordovician of the Siljan district, Sweden;
V, Notes on Swedish Ahtiella species. Bull. Geol. Inst. Univ. of Uppsala, 33: 511-526,
pis. 1-2.
HICKS, H. 1875. On the Succession of the Ancient Rocks in the vicinity of St. David's,
Pembrokeshire, with special reference to those of the Arenig and Llandeilo Groups, and
their Fossil Contents. Quart. J. geol. Soc. Lond., 31 : 167-195, pis. 8-n.
HOLM, G. 1886. III. Illaeniden. In Schmidt, F. 1886. Revision der Ostbaltischen
Trilobiten. Acad. impeviale Sci. St. Petersbourg, Mem., 7 : no. 33, 173 pp., 12 pis.
MACGREGOR, A. R. 1961. Upper Llandeilo brachiopods from the Berwyn Hills, North Wales.
Palaeontology, London, 4 : 177-209, pis. 19-23.
MATLEY, C. A. 1912. Notes on Orthis carausii (Salter MS) Davidson and O. calligramma,
var. proava Salter. Mem. Geol. Surv. G.B., Summary of Progress for 1911: Appendix 3,
78-79.
MOORE, R. C. 1959. Treatise on Invertebrate Palaeontology. Part O. Arthropoda I. xix +
560 pp., 415 figs. Lawrence & Meriden.
OPIK, A. A. 1932. tiber die Plectellinen. Publ. Geol. Inst. Univ. Tartu, 28 : 1-85, pis. 1-12.
J933- Uber Plectamboniten. Publ. Geol. Inst. Univ. Tartu, 31 : 1-79, pis. 1-12.
1934- Uber Klitamboniten. Publ. Geol. Inst. Univ. Tartu, 39 : 1-239, pis. 1-48.
1939- Brachiopoden und Ostracoden aus dem Expansusschieffer norwegens. Norsk.
Geol. Tidsskr., Oslo, 19 : 117-142, pis. 1-6.
RAYMOND, P. E., & BARTON, D. C. 1913. A revision of the American species of Ceraurus.
Bull. Mus. Comp. Zool. Harvard, Cambridge, Mass., 54 : 1-180, pis. 1-2.
REED, F. R. C. 1904-06. The lower Palaeozoic Trilobites of the Girvan District, Ayrshire.
186 pp., 20 pis. Palaeontogr. Soc. [Monogr.], London : 1-186, pis. 1-20.
1941. A new genus of trilobites and other fossils from Girvan. Geol. Mag., Lond., 78 :
268-278, pi. 5.
SALTER, J. W. 1866. On the Fossils of North Wales. Appendix in Ramsay, A. C. 1866.
The Geology of North Wales. Mem. Geol. Surv., G.B., London, 3 : viii + 381 pp., 28
pis., map.
SCHUCHERT, C. & COOPER, G. A. 1932. Brachiopod genera of the suborders Orthoidea and
Pentameroidea. Mem. Peabody Mus. Yale, 4 : 1-270, pis. A, 1-29.
SHIRLEY, J. 1936. Some British trilobites of the family Calymenidae. Quart. J. geol. Soc.
Lond., 92 : 384-422, pis. 29-31.
SINCLAIR, G. W. 1949. The Ordovician trilobite Eobronteus (North America and Europe).
J. Paleont., Tulsa, 23 : 45-56, pis. 12-14.
SNAJDR, M. 1960. Studie o celedi Scutelluidae (trilobitae) — A study of the family Scutel-
luidae (Trilobitae). Ustred. Ustav. Geol. Czechoslovakia, Rozpravy, 26 : 1-264.
SPJELDNAES, N. 1957. The Middle Ordovician of the Oslo region, Norway, 8. Brachiopods
of the suborder Strophomenoidea. Norsk. Geol. Tidsskr., Bergen, 37 : 1-214, pls- 1-14-
TWENHOFEL, W. H. et al. 1954. Correlation of the Ordovician formations of North America.
Bull. Geol. Soc. Amer., New York, 65 : 247-298.
ULRICH, E. O. & COOPER, G. A. 1938. Ozarkian and Canadian Brachiopoda. Geol. Soc.
Amer., New York, Special Paper 13 : 1-323, 57 pis.
WARBURG, E. 1925. The Trilobites of the Leptaena Limestone in Dalarne with a discussion
of the zoological position and the classification of the Trilobita. Bull. Geol. Inst. Univ.
Uppsala, 17 : 1-446, pis. i-n.
WHITTARD, W. F. 1940. The Ordovician Trilobite fauna of the Shelve-Corndon district,
West Shropshire. Part I. Ann. Mag. Nat. Hist., London (II), 5 : 153-172, pis. 5-6.
— 1956-64. The Ordovician trilobites of the Shelve Inlier, West Shropshire, 1-7. Palae-
ontogr. Soc. [Monogr.], London : 1-264, P^8- I-45-
WHITTINGTON, H. B. 1966. Trilobites of the Henllan Ash, Arenig Series, Merioneth. Bull.
Brit. Mus. (Nat. Hist.), Geol., London, 11 : 491-505, pis. 1-5.
WHITTINGTON, H. B. & EVITT, W. R. 1953. Silicified middle Ordovician trilobites. Geol.
Soc. Amer., New York, Mem. 59 : 1-137, 33 pls-
AND TRILOBITES OF ANGLESEY 199
WHITTINGTON, H. B. & WILLIAMS, A. 1955. The fauna of the Derfel Limestone of the Arenig
district, North Wales. Philos. Trans., London (B), 238 : 397-430, pis. 38-40.
WILLIAMS, A. 1962. The Barr and lower Ardmillan series (Caradoc) of the Girvan district,
South-west Ayrshire, with descriptions of the Brachiopoda. Mem. Geol. Soc. Land.,
3 : 1-267, 2O pls-
PLATE i
Hesperonomiella carmelensis sp. nov.
Carmel Formation, sandstones 50 yds. north-east of Prys-owain-bach, Carmel.
FIG. i. Latex cast of ventral interior. 66.30531. xi'4-
FIG. 2. Latex cast of ventral interior. 66.30530. Xi-5-
FIG. 3. Internal mould of pedicle valve. 66.3O532a. Xi'5-
FIG. 4. Holotype, latex cast of dorsal interior. 66.30529. x 1-5.
FIG. 5. Latex cast of ventral exterior. 66.305320. Xi-6.
FIG. 6. Latex cast of dorsal exterior. 66.30533. x 1-3.
Monorthis typis gen. et sp. nov.
Treiorwerth Formation, sandstone 300 yds. south-east of Ffynnon-y-mab, Trefor.
FIGS. 7, 8. Holotype, internal mould and latex cast of brachial valve. 66.30534. X3'4-
FIG. 9 Latex cast of dorsal interior. 66-3O535a. X47-
FIG. 10. Latex cast of dorsal exterior. 66.30535^ X3'2.
FIGS, ii, 12. Internal mould and latex cast of pedicle valve. 66.3O536a. X3'2.
FIG. 13. Latex cast of ventral exterior. 66.30536^ X3-2.
Orthambonites(l] sp. (i)
Nantannog Formation, gritty shales 220 yds. west of Fferam-uchaf, Llanbabo.
FIGS. 14, 17. Latex cast and mould of dorsal interior. Af.i3g8. X4-o, X2-5-
FIG. 16. Latex cast of dorsal exterior. Af.i399. X4-o.
Orthambonites (?) sp. (2)
Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.
FIG. 15. Latex cast of ventral interior. 66.30510. X3'3-
FIGS. 18, 19. Internal mould and latex cast of pedicle valve. 66.3O5iia. X2-9.
FIG. 20. Latex cast of ventral exterior. 66. 3051 ib. x 2-9.
Lenorthis proava (Salter)
Carmel Formation, sandstones 50 yds. north-east of Prys-owain-bach, Carmel.
FIG. 21. Internal mould of brachial valve. 66.30512. X2-3-
Bull. Er. Mus. nat. Hist. (Geol.) 16, 4
PLATE i
GEOL. l6, 4.
PLATE 2
Lenorthis proava (Salter)
Carmel Formation, sandstones 50 yds. north-east of Prys-owain-bach, Carmel.
FIG. i. Latex cast of dorsal interior. 66.30512. X2-I.
FIG. 2. Latex cast of dorsal interior. BB-3O5i5a. X2-2.
FIG. 4. Latex cast of dorsal exterior. BB.3O5i5b. X2-I.
FIG. 5. Latex cast of ventral exterior. 66.305135. X2-o.
FIG. 7. Latex cast of ventral interior. 66.30514. X2-8.
FIG. 8. Latex cast of ventral interior. B6.3O5i3a. X2-2.
Carmel Formation, sandstones 130 yds. north-west of Ty-hen, Treiorwerth.
FIGS. 3, 6. Internal mould and latex cast of pedicle valve. Af.i337- X2~4.
Cyrtonotella sp. (i)
Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.
FIGS. 9, 13. Internal mould and latex cast of brachial valve. 66.3O52ia. x 5-0.
FIG. 10. Latex cast of dorsal exterior. 66.30521^ X5-o.
Lenorthis sp.
Bod Deiniol Formation, grits in temporary excavation 50 yds. north of Ty-bach cottage,
6od Deiniol.
FIG. ii. Latex cast of dorsal interior. 66.30602. X2-i.
FIG. 12. Latex cast of ventral interior. 66. 30601 a. X2>7.
Cyrtonotella sp. (2)
Garn Formation, limestone blocks in breccia beds, Porth-Padrig, Mynachdy.
FIG. 14. Exterior of brachial valve. 66.30523. X2-4.
FIG. 15. Latex cast of dorsal exterior. 66.30524. X2-3.
FIG. 16. Exterior of pedicle valve. 66.30522. X3-2.
Pleurorthis costatus sp. nov.
Treiorwerth Formation, sandstones 300 yds. south-east of Ffynnon-y-mab, Trefor.
FIGS. 17, 18. Holotype, internal mould and latex cast of brachial valve. 66.30516. x 2-2.
FIG. 19. Latex cast of dorsal exterior. 66.30555^ X 3-3.
Bull. Br. Mm. nat. Hist. (Geol.) 16, 4
PLATE a
19
PLATE 3
Pleurorthis costatus sp. nov.
Treiorwerth Formation, sandstones 300 yds. south-east of Ffynnon-y-mab, Trefor.
FIGS, i, 2. Internal mould and latex cast of pedicle valve. 63.30518. x 2-2.
FIGS. 3, 4. Internal mould and latex cast of pedicle valve. "BB.^o^ija. X2-3.
FIG. 6. Latex cast of ventral exterior. BB. 30517!). X 2-3.
Nicolella hutnilis Williams
Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.
FIG. 5. Latex cast of dorsal interior. BB.3O5iQa. X3'i.
FIG. 7. Latex cast of dorsal exterior. BB. 30519^ X3'i.
FIG. 8. Latex cast of dorsal exterior. BB.3O52ob. X3'3-
FIG. 9. Internal mould of brachial valve. BB.3O52oa. X3'i.
Panderina lamellosa sp. nov.
Treiorwerth Formation, sandstones 300 yds. south-east of Ffynnon-y-mab, Trefor.
FIG. 10. Latex cast of dorsal interior. BB.3O528a. X4-2.
FIGS, ii, 12. Holotype, internal mould and latex cast of brachial valve. BB.3O525a. X4'2.
FIG. 13. Latex cast of dorsal exterior. BB. 30528^ X3-o.
FIG. 14. Holotype, latex cast of dorsal exterior. BB.3O525b. x 4-0.
FIGS. 15, 16. Latex cast and internal mould of pedicle valve. BB.3O526a. X5'5-
FIG. 17. Latex cast of ventral exterior. 66.30527^ X3-2.
FIG. 18. Latex cast of ventral interior. BB.30527a. X4'3.
Ptychopleurella sp. (i)
Nantannog Formation, fine sandstones and shales 190 yds. south-east of Fferam-uchaf farm,
Llanbabo.
FIG. 19. Latex cast of ventral interior. BB.3O537a. X4'i.
FIG. 20. External mould of pedicle valve. 66.30537^ X4-6.
FIGS. 21, 22. Internal mould and latex cast of brachial valve. BB.3O538a. X4'5-
FIG. 23. Latex cast of dorsal exterior. BB. 30538^ X4'5.
Bull. Br. Mus. nat. Hist. (Geol.) 16, 4
PLATE 3
* •
PLATE 4
Ptychopleurella sp. (2)
Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.
FIG. i. Internal mould of brachial valve. BB.3O53ga. X3'5.
FIGS. 2, 3. Internal mould and latex cast of pedicle valve. BB.3O54oa. X4'i.
FIG. 5. Fragment of external mould of pedicle valve. BB. 30540^ X4-o.
Dolerorthis cf. tenuicostata Williams
Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.
FIG. 4. Latex cast of ventral exterior. 66.30541^ X3-i.
FIGS. 6, 7. Internal mould latex cast of pedicle valve. BB.3O54ia. x 2-6, x 3-1.
Plaesiomys cf. robusta (Bancroft)
Crewyn Formation, grits 420 yds. west-south-west of Ysgubor-gader, Mynachdy.
FIG. 8. Latex cast of dorsal exterior. 66.30543^ X2-o.
FIG. 9. Latex cast of dorsal interior. BB.3O543a. x 2-2.
FIG. 10. Internal mould of pedicle valve. BB.3O544a. x 1-7.
FIG. n. External mould of pedicle valve. 66.30545^ x 1-7.
FIG. 12. Internal mould of pedicle valve. BB.3O545a. xi-y.
Plaesiomys (Dinorthis) sp.
Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.
FIGS. 13, 15. Internal mould and latex cast of pedicle valve. BB.3O542a. X2-6.
FIG. 14. Latex cast of ventral exterior. BB. 30542^ X 3-2.
Fleet ort his (?) sp.
Nantannog Formation, gritty shales 250 yds. west-south-west of Fferam-uchaf, Llanbabo.
FIG. 16. Internal mould of pedicle valve. Af.i377. X4-o.
FIG. 19. Internal mould of pedicle valve. Af.i462. X2-g.
Platystrophia precedens inajor Williams
Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.
FIG. 17. Latex cast of ventral interior. BB.3O546a. X2-2.
FIG. 18. Latex cast of ventral exterior. BB. 30546^ X2-o.
Bull. BY. Mus, nat. Hist. (Geol.) 16, 4
PLATE 4
18
19
PLATE 5
Skenidioides sp. (i)
Treiorwerth Formation, sandstones 300 yds. south-east of Ffynnon-y-mab, Trefor.
FIG. i. Internal mould of pedicle valve. 66.30547. x 7-7.
FIG. 2. Internal mould of brachial valve. 66.30548. x6-i.
Skenidioides sp. (2)
Nantannog Formation, fine sandstones and shales 190 yds. south-east of Fferam-uchaf, Llanbabo.
FIG. 3. Internal mould of brachial valve. 66.30549a. x6«5.
FIG. 4. Internal mould of pedicle valve. 66.3O55oa. X7-6.
FIG. 5. External mould of brachial valve. 88.30549^ X6-5.
Paurorthis(l) sp.
6od Deiniol Formation, grits in temporary excavation 50 yds. north of Ty-bach cottage,
6od Deiniol.
FIGS. 6, 7. Internal mould and latex cast of pedicle valve. 66.3o6o3a. x 2-5.
FIG. 8. Latex cast of ventral interior. 66.3o6o4a. X2-5-
FIG. 9. Latex cast of ventral exterior. 66.30604^ x 2-5.
DaliutmellaC?) sp.
Crewyn Formation, grits 420 yds. west-south-west of Ysgubor-gader, Mynachdy.
FIG. 10. Latex cast of brachial exterior. 66.30568. x 2-5.
FIG. ii. Latex cast of ventral exterior. 66.30569. X2-7-
Onniella(l] sp.
Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.
FIG. 12. Internal mould of pedicle valve. B8.3O57oa. xyj.
FIG. 13. Latex cast of ventral exterior. 88.30570^ X3-Q.
FIG. 14. Internal mould of brachial valve. 68.30571. X4-g.
Horderleyella(?) sp.
Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.
FIG. 15. Internal mould of pedicle valve. 66.30572. X2-g.
Harknessella sp.
Garn Formation, limestone block in breccia bed, 300 yds. east-south-east of the summit
of Mynydd-y-garn.
FIG. 16. Exterior of pedicle valve. Af.i492. X3-o.
Salopia salteri gracilis Williams
Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.
FIGS. 17, 18. Internal mould and latex cast of brachial valve. 66.30573. X3*9, X4'i.
Rhynchorthis rotundus gen. et sp. nov.
Treiorwerth Formation, sandstones 300 yds. south-east of Ffynnon-y-mab, Trefor.
FIGS. 19, 20. Holotype, internal mould and latex cast of brachial valve. 66.30551.
X2-9, X3-5-
FIGS. 21, 22. Internal mould and latex cast of brachial valve. 88.30552. X3'4, xj-y.
FIGS. 23, 25. Internal mould and latex cast of pedicle valve. 68.30556. X3'4, X3'i.
FIG. 24. Internal mould of pedicle valve. 88.30554. X3-2.
FIG. 26. Internal mould of brachial valve. 88.30553. X3-o.
Bull. Br. Mus. nat. Hist. (Geol.) 16, 4
PLATE 5
26
PLATE 6
Tritoechia sp.
Treiorwerth Formation, sandstones 300 yds south-east of Ffynnon-y-mab, Trefor.
FIG. i. Latex cast of ventral interior. BB.3O55ya. X2-2.
FIG. 2. Latex cast of ventral interior, and exterior of interarea, posterior view. BB.3O55ya.
X2-2.
FIGS. 3, 5. Latex cast of ventral exterior, posterior and ventral views. 66.305575. x 2-o.
Clitambonites(?) sp.
Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.
FIG. 4. Latex cast of dorsal exterior. 66.30558. xi'4-
Ilmarinia sp.
Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.
FIGS. 6, 7. Internal mould of pedicle valve, ventral and posterior views. BB-3O559a. x 3-1.
Apomatella(>) sp.
6od Deiniol Formation, grits in temporary excavation 50 yds. north of Ty-bach cottage,
6od Deiniol.
FIG. 8. Latex cast of ventral interior. 66.3o6o5a. X3-o.
FIG. 9. Latex cast of ventral exterior, posterior view. 66.306055. X3-o.
FIG. 10. Latex cast of ventral exterior, posterior view. 66-3o6o6b. X2-3.
FIG. ii. Latex cast of ventral interior. 66.3o6o6a. X2-4.
Antigonambonites pyramidalis sp. nov.
Treiorwerth Formation, sandstones 300 yds. south-east of Ffynnon-y-mab, Trefor.
FIG. 12. Holotype, latex cast of dorsal interior. BB.3O56ia. X4-i.
FIG. 13. Holotype, latex cast of dorsal exterior. 66.30561^ X4'4-
FIGS. 14, 15. Latex cast and internal mould of brachial valve. 66.30563. x 2-8, X2-2.
FIGS. 16, 17. Internal mould and latex cast of pedicle valve. 66.30564. X3'3, X3'5.
FIG. 18. Internal mould of pedicle valve. 66.30562. x 4-0.
Kullervo aff . panderi (Opik)
Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.
FIGS. 19, 20. Internal mould and latex cast of brachial valve. 66.3O567a. x 4-0.
FIG. 21. Latex cast of dorsal exterior. 66.30567^ x 4-0.
FIG. 22. Internal mould of pedicle valve. 66.30565. X2-5.
Bull. Br. Mus. nat. Hist. (Geol.) 16, 4
PLATE 6
22
PLATE 7
Kullervo ail pander i (Opik)
Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.
FIG. i. Latex cast of ventral interior. 36.30566. X5*i.
Estlandia(?) sp.
Berw-uchaf Grits, 90 yds. north of Bwlch-gwyn farm, Holland Arms.
FIG. 2. Latex cast of ventral interior. Af.238. X5-2.
FIG. 3. Latex cast of ventral exterior. Af.225. X5-2.
FIGS. 4, 9. Internal mould and latex cast of brachial valve. Af.2i4. X5-o.
FIGS. 6, 7. Internal mould and latex cast of brachial valve. BB.3o56oa. x 7-7.
FIG. 8. Latex cast of dorsal exterior. BB. 30560^ X 7-7.
Clitambonitid gen. indet.
Bod Deiniol Formation, grits in temporary excavation 50 yds. north of Ty-bach cottage,
Bod Deiniol.
FIG. 5. Latex cast of dorsal interior. BB-3o6o8a. X 2-0.
FIGS. 10, ii. Latex cast of ventral interior, dorsal and anterior views. 66.30607. X3-o.
Ahtiella concava sp. nov.
Bod Deiniol Formation, grits in temporary excavation 50 yds. north of Ty-bach cottage,
Bod Deiniol.
FIG. 13. Latex cast of dorsal interior. BB.3o6i6a. X2-4-
FIG. 12. Latex cast of dorsal interior, cardinalia. BB.3o6i6a. x 3-0.
FIG. 14. Holotype, latex cast of ventral interior. BB.3o6i5a. xi-g.
FIGS. 15, 1 8. Holotype, latex cast of ventral exterior, ventral and posterior views. BB.
3o6i5b. xi -9-
FIGS. 16, 19. Latex cast of dorsal interior, ventral and oblique posterior views. BB.
3o6i8a. X2-4.
FIG. 22. Latex cast of dorsal exterior. BB-3o6i6b. x 2-3.
FIG. 17. Latex cast of dorsal interior. BB.3o6i7a. X2-2.
FIG. 20. Latex cast of ventral interior. BB-3o6i9a. X2-3-
FIG. 21. Latex cast of ventral exterior. BB.3o6i9b. X2-2.
Bull. Br. Mus. naf. Hist. (Geol.) 16, 4
PLATE 8
Ahtiella quadrata sp. nov.
Torllwyn Formation, sandstones 50 ft. above the base of the succession, on
the north side of the faulted syncline, 45 yds. north of Ogof Gynfor, Llanbadrig.
FIG. i. Latex cast of dorsal interior. BB.3o6i3a. X2-2.
FIG. 4. Latex cast of dorsal exterior. BB.3o6i3b. X2-o.
FIG. 2. Latex cast of ventral interior. BB.3o6na. X2-o.
FIG. 3. Latex cast of ventral exterior. BB.3o6nb. xa-o.
FIG. 5. Latex cast of dorsal interior. BB.3o6i2a. X2-2.
FIG. 6. Latex cast of dorsal exterior. BB.3o6i2b. xi-g.
FIG. 7. Latex cast of dorsal interior. BB.3o6i4a. x 2-3.
FIG. 8. Holotype, latex cast of ventral interior. 66.30609. x 2-0.
FIG. 9. Latex cast of ventral interior. 66.30610. x 2-0.
Reinversella tnonensis gen. et sp. nov.
Treiorwerth Formation, sandstones 300 yds. south-east of Ffynnon-y-mab, Trefor.
FIGS. 10, ii. Holotype, internal mould and latex cast of brachial valve. 66.3O574a. x 1-6.
FIG. 12. Holotype latex cast of dorsal exterior. 66.30574^ xi-6.
FIGS. 13, 14. Internal mould and latex cast of pedicle valve. 66.3O575a. x 1-9, Xi'7-
FIG. 15. Latex cast of ventral exterior. 66.30575^ X2-2.
FIG. 16. Internal mould of brachial valve. 66.3O57&a. X2-i.
FIG. 17. Latex cast of dorsal exterior. 66.30576b. x 2-2.
Bull. Br. Mus. nat. Hist. (Geol.) 16, 4
ill
PLATE 8
10
17
PLATE 9
Palaeostrophomena(?) sp.
Garn Formation, limestone blocks in breccia beds at Forth Padrig, Mynachdy.
FIG. i. Exterior of pedicle(?) valve. BB.3O58ia. X2-2.
Sericoidea abdita Williams
Tandinas Shales, by the shore 100 yds. west of the pier, Careg-onen.
FIG. 3. Internal mould of brachial valve with shell material adhering. 66.30588. xyi.
FIG. 6. Interior of brachial valve. 66.30587. X7'3.
Palaeostrophomena sp.
Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.
FIG. 2. Latex cast of ventral interior. 8B.3O57Qa. X3-2.
FIGS. 4, 5. Internal mould and latex cast of brachial valve. 66.30580. x 3-0.
Leptestiina derfelensis (Jones)
Tandinas Shales, by the track 50 yds. west of Tandinas Quarry, Careg-onen.
FIGS. 7, 8. Internal mould and latex cast of pedicle valve. 66.30577. X4-o.
FIG. 9. Latex cast of dorsal interior. 66.30578. X4'4-
Bilobia aff. musca (Opik)
Llanbabo Formation, Llanbabo Church Grits, 180 yds. east of Fferam-uchaf, Llanbabo.
FIGS. 10, ii. Internal mould of pedicle valve, ventral and posterior views. 66.30582.
X3-o, X4-o.
FIG. 12. Latex cast of ventral interior. 66.30582. X3-o.
FIG. 13. Internal mould of part of brachial valve. 66.30583. x 3-3.
Eoplectodonta lenis Williams
Llanbabo Formation, Llanbabo Church Grits, Church Quarry, Llanbabo.
FIGS. 14, 15. Internal mould and latex cast of pedicle valve. 68.3O584a. x 4-0, x 3-7.
FIG. 16. Internal mould of brachial valve. 66.30585a. X4-i.
FIG. 17. Latex cast of dorsal exterior. 68.30585^ X4'i.
FIG. 18. Latex cast of dorsal exterior. 86.30586. X4'5-
Bull. BY. Mus. nat. Hist. (Geol.) 16, 4
PLATE 9
10
16
GEOL. 1 6, 4.
PLATE 10
Ptychoglyptus sp.
Garn Formation, limestone blocks in breccia beds at Forth Padrig, Mynachdy.
FIG. i. Exterior of brachial valve. 66.30589. X 4-4.
FIG. 2. Exterior of pedicle valve. 66.30590. X4'4.
Leptaena sp.
Llanbabo Formation, Llanbabo Church Grits, 180 yds. east of Fferam-uchaf, Llanbabo.
FIG. 3. Latex cast of dorsal interior. 66.30592. X3'2.
FIGS. 4, 5. Internal mould and latex cast of pedicle valve. 66.30591. X2-2.
FIG. 6. Internal mould of brachial valve. 66.30593. X4'5-
Dactylogonia sp.
Nantannog Formation, fine sandstones and shales 190 yds. south-east of Fferam-uchaf farm,
Llanbabo.
FIGS. 7, 8. Latex cast and internal mould of brachial valve. 66.3O596a. X5-6, X4'6.
Kiaeromena(l] sp.
Garn Formation, limestone blocks in breccia beds, Forth Padrig, Mynachdy.
FIG. 9. Exterior of brachial(P) valve. 66.30595. x 2-9.
FIG. 10. Exterior of pedicle(?) valve. 66.30594. X3'i.
Rectotrophia globularis gen. et sp. nov.
Treiorwerth Formation, sandstones 300 yds. south-east of Ffynnon-y-mab, Trefor.
FIGS, ii, 12. Internal mould of brachial valve, dorsal and lateral views. Af.i436. X3-6.
FIG. 13. Latex cast of internal mould of brachial valve. Af.i436. X4-y.
FIGS. 14, 15. Holotype, internal mould of pedicle valve, ventral and lateral views. Af . 1436.
X3-i.
FIG. 16. Holotype, latex cast of ventral interior. Af.i436. X4'i.
FIG. 17. Internal mould of brachial valve. Af.i442. X4'3-
Order uncertain
Torllwyn Formation, sandstones 50 ft. above the base of the succession, on the
north side of the faulted syncline, 45 yds. north of Ogof Gynfor, Llanbadrig.
FIGS. 18, 19. Internal mould of brachial valve, posterior and dorsal views. 66.5579ia.
xi-5.
FIG. 21. Latex cast of brachial valve. 66.5579^. X2-2.
FIGS. 20, 22. Internal mould and latex cast of pedicle valve. 66-55792a. x 1-8.
FIG. 23. Latex cast of dorsal exterior. 86.55791^ X2-i.
FIG. 24. Latex cast of ventral exterior. 86.55792^ X 1-5.
Bull. Br. Mus. nat. Hist. (Geol.) 16, 4
PLATE 10
-»
PLATE ii
Porambonites (s.s.) sp.
Treiorwerth Formation, sandstones 300 yds. south-east of Ffynnon-y-mab, Trefor.
FIGS, i, 2. Internal mould and latex cast of pedicle valve. BB.3O598a. x 1-7.
FIG. 3. Internal mould of brachial valve. BB.3O59ga. Xi-5-
FIGS. 4, 8. Latex cast of dorsal interior, dorsal and anterior views. BB.3O59ga. x 1-3.
FIGS. 5, 6. Latex cast and internal mould of brachial valve. BB. 30600. X2-4, xa-2.
Camerella sp.
Garn Formation, limestone blocks in breccia beds at Forth Padrig, Mynachdy.
FIGS. 7, 9, 10, ii. Complete shell, anterior .dorsal, lateral and ventral views. 66.30597.
X4-8.
Metacamerella cf. balcletchiensis (Davidson)
Garn Formation, limestone blocks in breccia beds at Forth Padrig, Mynachdy.
FIGS. 12, 13, 14. Complete shell, dorsal, lateral and anterior views. Af.i59o. X 1-5, Xi'5,
X2-0.
Monella perplexa gen. et sp. nov.
Carmel Formation, sandstone 400 yds. north of Bryn Gollen Uchaf, Llanerchymedd.
FIGS. 16, 19. Holotype, internal mould of entire exoskeleton, dorsal and anterior views.
Af.827. X3-o.
FIG. 15. Internal mould of cranidium. Af.836. x 2-4.
FIG. 17. Internal mould of cranidium. Af.834. X2-5.
FIG. 20. Internal mould of pygidium. Af.839. X3-i.
Carmel Formation, sandstones 50 yds. north-east of Prys-owain-bach, Carmel.
FIGS. 1 8, 21. Latex casts of external mould of cranidium and one librigena, and incomplete
thorax and pygidium. In. 58290. xi-o.
Bull. Br. Mus. nat. Hist. (Geol.) 16, 4
/i
PLATE ii
PLATE 12
Ogygiocaris selwynii (Salter)
Carmel Formation, sandstones 400 yds. north of Bryn Gollen Uchaf, Llanerchymedd.
FIG. i. Internal mould of cranidium. Af.823_ x i-i.
FIG. 2. Internal mould of cranidium. Af.842. x i-o.
FIG. 5. Internal mould of pygidium. Af.Sao. xi-o.
FIG. 6. Internal mould of pygidium. Af .821. x i-o.
Protobronteus greenly i sp. nov.
Garn Formation, limestone blocks in breccia beds, Forth Padrig, Mynachdy.
FIG. 3. Incomplete cranidium. In. 58292. X2'3.
FIG. 4. Internal mould of librigena. In.58293a. x i-i.
FIG. 7. Holotype, incomplete cranidium. In. 58291. xi-o.
Illaenus sp.
Garn Formation, limestone blocks in breccia beds, Forth Padrig, Mynachdy.
FIGS. 8, ii, 15. Internal mould of cranidium, anterior, dorsal and oblique views. 111.58294.
X2-7.
FIGS. 9, 10. Internal mould of pygidium, with doublure partially revealed, lateral and dorsal
views. In. 58295. xi'4-
FIGS. 12, 13. Internal mould of pygidium, with some skeletal material adhering, dorsal
and lateral views. In. 58296. xi-i.
Stenopareia cf. linnarssoni (Holm)
Garn Formation, limestone blocks in breccia beds, Forth Padrig, Mynachdy.
FIG. 14. Rostral plate. In. 58300. X2-2.
FIG. 16. Internal mould of librigena. ^.58299. X2-o.
FIG. 17. Internal mould of pygidium, showing the doublure. In. 58302. X2-2.
FIGS. 1 8, 19. Internal mould of incomplete pygidium, with skeletal material adhering,
dorsal and lateral views. In. 5 8301. x i-i.
FIGS. 20, 21. Internal mould of cranidium, anterior and dorsal views. ^.58297. X2-i,
X3-o.
FIGS. 22, 23. Internal mould of cranidium, with some skeletal material adhering, anterior
and dorsal views. In. 58298. xa-i.
Bull. Br. Mus. not. Hist. (Geol.) 16, 4
PLATE 12
23
PLATE 13
Selenoharpes(?) sp.
Garn Formation, limestone blocks in breccia beds, Forth Padrig, Mynachdy.
FIGS, i, 5, 6. Cranidium, dorsal, lateral and anterior views. In. 58303. x 1-6.
FIG. 2. Cranidium, detail of fixigena and brim. ^.58303. X 2-5.
Bergatnia(?) sp.
Shales, D. bifidus zone, quarry 100 yds. north of Gwredog-uchaf, Rhodogeidio.
FIG. 3. External mould of complete dorsal carapace. In. 58305^ X 8-0.
FIG. 4. Internal mould of dorsal carapace lacking the librigenae. In. 58306. X 1-3.
FIGS. 9, 13. External and internal moulds of cranidium and pygidium. In. 58304.
Atnpyx sp. (i)
Carmel Formation, sandstones on scarp west of Bryn Gollen Uchaf, Llanerchymedd.
FIG. 8. Internal mould of cranidium. Af.824- X 3-8.
Atnpyx sp. (2)
Tandinas Shales, by the track 50 yds. west of Tandinas Quarry, Careg-onen.
FIG. 7. External mould of cranidium. In. 58308. X3-2.
FIG. 10. Internal mould of thoracic segments and pygidium. Af.3653. X2-o.
Tandinas Shales, on the shore by the power house, 100 yds. west of the pier.
FIG. ii. Internal mould of cranidium. In.583O7a. Xi-j.
FIG. 12. Latex cast of external mould of pygidium. In. 58309. X3-o.
Ceraurinella sp.
Garn Formation, limestone blocks in breccia beds, Forth Padrig, Mynachdy.
FIG. 14. Incomplete cranidium. In. 5 83 12. X2-2.
FIG. 15. Glabella. In. 58311. X3-2.
FIG. 16. Glabella. In. 58310. X3-2.
FIG. 17. Hypostome. ^.58315. x 2-4.
FIG. 18. Latex cast of external mould of thoracic segment. In. 58316. X 2-1.
FIG. 19. Thoracic segment. ^.58317. X2-2.
FIG. 20. Pygidium. In. 58318. X4-o.
FIG. 21. Hypostome. In. 58313. xi-6.
FIG. 22. Hypostome. In. 58314. X 3-2.
Bull. BY. Mus. nat. Hist. (Geol.) 16, 4
. . ~._..
PLATE 14
Sphaerexochus sp.
Tandinas Shales, on the shore by the power house, 100 yds. west of the pier, Careg-onen.
FIGS, i, 2. Cranidium, dorsal and oblique lateral views. ^.58319. X3-2.
Pliomerops sp.
Garn Formation, limestone blocks in breccia beds, Forth Padrig, Mynachdy.
FIG. 3. Hypostome. In. 58321. xi-8.
FIG. 4. Incomplete cranidium. In. 58320. X2-2.
FIG. 6. Incomplete pygidium. In. 58322. Xi-3-
FIG. 7. Latex cast of external mould of pygidium. In. 58323^ X2-o.
Placoparia sp.
Shales on the shore at Porth-y-gwichiaid, 80 yds. north of the streamlet.
FIG. 5. Complete dorsal carapace, lacking the librigenae. M.i^ig. X2-6.
Calymenid (s.l.) sp.
Garn Formation, limestone blocks in breccia beds, Forth Padrig, Mynachdy.
FIG. 8. Hypostome. In. 58324. X3'i.
FIGS. 9, 12, 13. Pygidium, dorsal, posterior and oblique lateral views. In. 58325. X2-8.
Neseuretus monensis (Shirley)
Carmel Formation, sandstones 120 yds. north-west of Chwaen-bach, Llanerchymedd.
FIG. ii. Internal mould of pygidium. In. 58327. x 1-7.
Carmel Formation, sandstones 440 yds. north of Ty-hen, Treiorwerth.
FIG. 16. Internal mould of pygidium. In.58326a. xi'7-
Arnphilichas sp. (i)
Garn Formation, limestone blocks in breccia beds, Porth Padrig, Mynachdy.
FIGS. 10, 14, 17. Cranidium, anterior, lateral and dorsal views. ^.58328. X2-o.
FIG. 15. Hypostome. In. 58329. X3'3-
Arnphilichas sp. (2)
Tandinas Shales, by the track 50 yds. west of Tandinas Quarry, Careg-onen.
FIGS. 18, 19. External mould and latex cast of cranidium. Af .3000. x 2-1.
Bull. Br. Mus. nat. Hist. (Geol.) 16, 4
PLATE 14
PRINTED IN GREAT BRITAIN
BY ADLARD & SON LIMITED
BARTHOLOMEW PRESS DORKING
\ *
THE CAUDAL SKELETON IN LOWER
LIASSIC PHOLIDOPHORID FISHES
C. PATTERSON
BULLETIN OF
THE BRITISH MUSEUM (NATURAL HISTORY)
GEOLOGY Vol. 16 No. 5
LONDON: 1968
THE CAUDAL SKELETON IN LOWER LIASSIC
PHOLIDOPHORID FISHES
BY
C. PATTERSON A
- <H''<\
British Museum (Natural History)
Pp. 201-239; 5 Plates; 12 Text-figures
BULLETIN OF
THE BRITISH MUSEUM (NATURAL HISTORY)
GEOLOGY Vol. 16 No. 5
LONDON: 1968
THE BULLETIN OF THE BRITISH MUSEUM
(NATURAL HISTORY), instituted in 1949, is
issued in five series corresponding to the Departments
of the Museum, and an Historical series.
Parts will appear at irregular intervals as they become
ready. Volumes will contain about three or four
hundred pages, and will not necessarily be completed
within one calendar year.
In 1965 a separate supplementary series of longer
papers was instituted, numbered serially for each
Department.
This paper is Vol. 16, No. 5 of the Geological
(Palaeontological) series. The abbreviated titles of
periodicals cited follow those of the World List of
Scientific Periodicals.
World List abbreviation :
Bull. Br. Mus. nat. Hist. (Geol.)
Trustees of the British Museum (Natural History) 1968
TRUSTEES OF
THE BRITISH MUSEUM (NATURAL HISTORY)
Issued 14 June, 1968 Price £i 125. 6d.
THE CAUDAL SKELETON IN LOWER LIASSIC
PHOLIDOPHORID FISHES
By COLIN PATTERSON
MS accepted May ijth 1967
CONTENTS
Page
I. INTRODUCTION ......... 203
II. DESCRIPTION .......... 204
(a) Distinction between ural and pre-ural structures . . 206
(b) The vertebral centra ....... 206
(c) The hypurals and haemal spines ..... 209
(d) The neural arches and neural spines . . . . 210
(e) The epurals . . . . . . . . 212
(f) The fin-rays . . . . . . . .214
(g) The squamation . . . . . . . . 215
III. DISCUSSION . . . . . . . . . . 218
(a) Comparison with chondrosteans, holosteans and teleosts . 218
(b) The homologies of the epurals . . . . . 220
(c) Uroneurals and urodermals . . . . . . 221
(i) The uroneurals . . . . . . . 221
(ii) The urodermals . . . . . . .229
(iii) The function of the uroneurals . . . . 231
(d) Definition of the Teleostei ...... 234
(e) Taxonomy and interrelationships of Lower Liassic Pholido-
phoridae ........ 235
IV. SUMMARY AND CONCLUSIONS . . . . . . . 236
V. REFERENCES ......... 237
ADDENDUM ......... 239
SYNOPSIS
The caudal vertebrae and the caudal skeleton and fin are described in Pholidophorus bechei,
Pholidolepis and Pholidophoropsis. The centra were formed by calcifications in the sheath of the
unconstricted notochord, and were diplospondylous in the middle part of the caudal region.
The caudal skeleton is strongly asymmetrical, resembling those of primitive actinopterygians
rather than teleosts. The uroneurals of teleosts are modified ural neural arches: the ural
neural arches are already considerably modified in pholidophorids. One or two urodermals,
relics of the rhombic scales of the caudal axis, persist in a few primitive teleosts. The functional
significance of changes in the tail at the pholidophorid/leptolepid transition is discussed, and a
new definition of the Teleostei, based on these changes, is proposed.
I. INTRODUCTION
DURING the last few years the caudal skeleton of teleost fishes has been shown to be
of great value in tracing relationships between and within major groups. This in-
terest in the caudal skeleton is due primarily to the work of Gosline (1960) who first
introduced a rational terminology for the various structures. Nybelin (1963), in a
superbly illustrated paper containing the first detailed illustrations of caudal struc-
tures in fossil teleosts, gave added precision to the terminology of the tail, and paid
GEOL. l6, 5. 22
204 CAUDAL SKELETON IN LOWER
particular attention to the nature of the " uroneurals ". Nybelin figured the caudal
skeleton in several Jurassic teleost forerunners including Leptolepis coryphaenoides,
L. normandica and L. dubia, but the structure of the tail in the ancestors of the
leptolepids, the pholidophorids, has so far remained unknown. During a visit to the
Royal Scottish Museum, Edinburgh, in October 1966, I came across a specimen from
the Lower Lias of Lyme Regis, Dorset, identifiable as Pholidophorus bechei, in
which the scales are missing, exposing a well preserved caudal endoskeleton. In
trying to interpret this specimen I have examined the British Museum (Natural
History) collections of Lower Lias pholidophorids, which have recently been revised
by Nybelin (1966), and found that the caudal skeleton is occasionally visible or can be
prepared in specimens of Pholidophorus bechei, Pholidolepis and Pholidophoropsis.
The primary purpose of the descriptions of caudal structures in these fishes which
follow is to settle the " uroneural/urodermal " question, but other points in the
structure of the caudal skeleton and fin in these pholidophorids throw light on the
evolution of teleosts and a discussion of these is added.
My best thanks are due to Prof. Orvar Nybelin, who has been most generous with
advice, with unpublished photographs of pholidophorid caudal skeletons and un-
published information on teleost caudal skeletons, and has read the manuscript of
this paper. Dr. P. H. Greenwood has also kindly read the paper in manuscript.
I am grateful to Drs. C. D. Waterson and R. S. Miles of the Royal Scottish Museum
for the loan of a specimen of Pholidophorus bechei, and to Mr. P. J. Green, who took
the photographs.
The abbreviation RSM refers to the Royal Scottish Museum, Edinburgh. Speci-
mens referred to by a number without prefix or with the prefix " P " are in the
Department of Palaeontology, British Museum (Natural History) ; the prefix
BMNH indicates dried skeletons in the Department of Zoology, British Museum
(Natural History).
II. DESCRIPTION
In this section the caudal skeleton is described in three pholidophorids from the
Lower Lias of Lyme Regis, Dorset, Pholidophorus bechei Agassiz, Pholidolepis
dorsetensis Nybelin, and Pholidophoropsis maculata Nybelin.
Pholidophorus bechei is the type species of the genus. The caudal skeleton is
visible in 19010 (PI. i, Text-fig, i : the skull of this specimen was figured by Rayner
1948, fig. 26), RSM 1888.61.73 (PL 3, fig. i; Text-figs 2 A, 5 A), P.34822 (Text-figs
26, 56) and P.4882O (Text-fig. 56). P. 154 (PI. 5, fig. i) and several other specimens
have also been used in preparing the description.
Pholidolepis dorsetensis Nybelin (1966 : 387) is the only species of a genus set up
by Nybelin for Lower Liassic pholidophorids differing from Pholidophorus principally
in reduction in the enamel covering of the dermal bones, loss of fulcra from all fins
except the caudal, and in the presence of thin, cycloid scales. Nybelin suggested
that Pholidolepis might be intermediate between Pholidophorus and Leptolepis.
The caudal skeleton is partially visible in several specimens of P. dorsetensis, the
best being P.6o67 (PL 2; Text-fig. 3), P.44709 (PL 3, fig. 2; Text-fig. 4A) and
P.939C (Text-fig. 4B).
LIASSIC PHOLIDOPHORID FISHES
205
206 CAUDAL SKELETON IN LOWER
The genus Pholidophoropsis Nybelin (1966 : 411) contains Lower Liassic pholido-
phorids in which the scales are thin and cycloid and the dermal bones with little
enamel as in Pholidolepis , but which in other respects resemble Pholidophoroides.
There are two species, P. caudalis (Woodward) and P. maculata Nybelin. In P.
caudalis the caudal skeleton is not well exposed in any available specimen, but the
caudal squamation is well shown in the holotype, 43055 (Text-fig. 8). The paratype
of P. maculata, P. 7582 (PI. 4; Text-fig. 6) has the caudal skeleton somewhat dis-
turbed but otherwise well preserved.
(a) Distinction between ural and pre-ural structures. Nybelin (1963 : 487) introduced
the distinction between pre-ural centra, carrying normal or little modified haemal
arches and spines, and ural centra, carrying hypurals. The boundary between these
is marked by the point at which the caudal artery and vein, carried within the
haemal arches of the pre-ural vertebrae, fork and pass lateral to the hypurals, which
do not have a median canal proximally. 19010, Pholidophorus bechei, is the only
available specimen in which the axial skeleton is preserved in the round. In this
specimen (PI. i ; Text-fig, i) the exit of the caudal vessels from the haemal canal
is marked by a horizontal groove (g.c.v.) on the first hypural (h j). Just below this
groove on the first hypural there is a peg-like process passing forwards and fitting in
a notch on the hind face of the first pre-ural haemal arch (hpu 1} . The succeeding
hypurals are without such a process while the two last haemal arches have a less
distinct process. A similar peg-like process can be recognized on the first hypural of
Leptolepis coryphaenoides and L. normandica (Nybelin 1963, text-figs 9, 10), L. dubia
(Text-fig. 10), Salmo, etc., and in pholidophorids it is a useful means of recognizing
the first hypural in specimens where the caudal skeleton is too crushed to show the
groove for the caudal vessels. In P.34822 (Text-fig. 2B) the groove for the caudal
vessels on the first hypural is partially covered, forming a canal anteriorly.
The validity of the ural/pre-ural dividing line as a morphological boundary is
supported by the fact that in pholidophorids the pre-ural neural arches are fused with
the neural spines into median structures while the ural neural arches are paired (p. 210).
(b) The vertebral centra. The vertebral column is best preserved in 19010, Pholido-
phorus bechei (PI. i; Text-fig, i). The notochord was unconstricted. Above and
below the space occupied by the notochord there is a series of calcifications in the
form of half -rings (n.c), normally lying opposite one another in dorso-ventral pairs
which meet or almost meet lateral to the notochord. The neural and haemal
arches, and in the middle part of the caudal region the independent dorsal and
ventral intercalaries (d.ic, v.ic; terminology of Schaeffer 1967), are applied to the
half-ring calcifications dorso-laterally and ventro-laterally, but do not cover them
laterally. As preserved, these calcifications (hemicentra) differ sharply from the
endochondral bone of the neural and haemal arches in their dark colour, dense,
fibrous texture and vertical striation (PI. i). In thin section the hemicentra differ
from the trabecular, sparsely cellular bone of the arches in being solid, without cell
spaces or vascular canals, and in containing many tangentially arranged fibres,
which presumably account for their dark colour and vertically striated appearance.
LIASSIC PHOLIDOPHORID FISHES
207
n.c
hi
TEXT -FIG. 2. Pholidophorus bechei Agassiz. The caudal skeleton as preserved in A, RSM
1888.61.73 (see also PL 3, fig. i); B, P. 34822. Details of the ural neural arches of
these specimens are shown in Text-fig. 5. In B the second hypural is missing, ep,
epurals ; g.c.v, groove for caudal vessels on first hypural ; h i, h 2, h 3, h 10, h 12, hypurals
1-12; hpu i, hpu 4, first and fourth pre-ural haemal spines; n.c, notochordal calcifications
(hemicentra) ; nc.u i, ventral hemicentrum of first ural centrum ; npu i, first pre-ural
neural arch; pph, postero-dorsal processes on heads of upper hypurals; una i, una 6, una 8,
first, sixth and eighth ural neural arches; v.ra, ventral caudal radials
2o8 CAUDAL SKELETON IN LOWER
In structure these hemicentra agree exactly with the centra of the Triassic pholido
pleurid Australosomus (Stensio 1932 : 174, pis 35-37). Stensio concluded that the
ring-like centra of Australosomus are chordal, not perichordal as are the centra of
most actinopterygians. Nielsen (1949 : 134, pi. 6) found that in one specimen of
Australosomus the small precentra in the diplospondylous middle part of the caudal
region consisted of independent dorsal and ventral half -rings, just as in P. bechei.
The structure and arrangement of the centra in P. bechei shows that, like the centra of
Australosomus, they are calcifications in the sheath of the notochord: this inter-
pretation is supported by the presence of ring-like calcifications in the sheath of the
notochord of larval Clupea (Ramanujam 1929 : 377) and by the recent discovery
(Frangois 1966 : 292) that in Salmo the first calcification of the centrum (in ontogeny)
is a median ventral crescentic calcification in the sheath of the notochord. In
Pholidophorus bechei and in Pholidophoropsis the dorsal and ventral hemicentra
appear to be separate throughout the vertebral column, but in Pholidolepis they tend
to fuse with each other to form complete rings (Text-fig. 4A).
In Pholidophorus bechei, Pholidophoropsis and Pholidolepis the vertebral column
is diplospondylous in the middle part of the caudal region, as it is in Australosomus
and many holosteans. In P. bechei (PI. i ; Text-fig, i) about twelve vertebrae are
diplospondylous, the majority of the caudal vertebrae. Passing forwards from the
tail, the last complete precentrum (prc) (carrying no neural or haemal spine,
Schaeffer 1967) lies in front of the sixth pre-ural centrum and in front of this there
are about seven more segments in which separate pre- and postcentra (poc) are de-
veloped. In front of the second to fifth pre-ural centra there are no independent
ventral intercalaries or ventral notochordal calcifications, but the dorsal intercalaries
remain free, all but the last with a small notochordal calcification. In Pholidolepis
(PI. 2; Text-fig. 3), although the vertebral column is never so well preserved as it is
in some specimens of P. bechei, the number of diplospondylous segments seem to be
about the same as in P. bechei : 38163 shows complete precentra in front of pre-ural
centra 7-15, though other specimens show fewer precentra. In Pholidophoropsis
there are at least five diplospondylous segments (pre-ural 6-10) in P.7582, P.
maculata. In these pholidophorids it is impossible to be certain whether the inter-
calaries fused with the neural and haemal arches or were absent in centra which are
not diplospondylous. Appearances in P. bechei (Text-fig, i) and Pholidolepis
(Text-fig. 3) suggest that the ventral intercalaries fuse with the haemal arch of the
centrum behind them, but it is quite possible that intercalaries were absent in mono-
spondylous segments, as they appear to be in teleosts.
In P. bechei the last complete centrum, with both dorsal and ventral notochordal
calcifications, is the second pre-ural in 19010 (Text-fig, i), the first pre-ural in RSM
1888.61.73 (Text-fig. 2A) and the first ural in P. 34822 (Text-fig. 2B) and other
specimens. In 19010 there is only a ventral hemicentrum in the first pre-ural
centrum, and in RSM 1888 . 61 . 73 there is only a ventral hemicentrum in the first
ural centrum, above the first hypural. In all specimens the notochord was uncal-
cified and unconstricted behind the first hypural, though the close approximation of
the heads of the hypurals and the neural arches in the posterior ural region (Text-
figs i, 2) shows that the notochord must have decreased in diameter very sharply.
LIASSIC PHOLIDOPHORID FISHES
209
hi
2mm
TEXT-FIG. 3. Pholidolepis dorsetensis Nybelin. The posterior part of the vertebral column
and the base of the caudal fin as preserved in P.6o6y (see also PL 2). b.f. epaxial basal
fulcra; d.ic, dorsal intercalaries ; ep 1-4, epurals; /./., fringing fulcra; h i, h 2, first and
second hypurals ; hpu i, haemal spine of first pre-ural centrum ; l.fr, expanded base of
lowermost fin-ray in upper caudal lobe; n.c, notochordal calcifications (hemicentra) ;
npu i, neural arch of first pre-ural centrum ; poc, prc, pu 7, postcentrum and precentrum
of seventh pre-ural vertebra; pph, postero-dorsal processes on heads of upper hypurals;
r.fr, reduced uppermost hypaxial fin-ray; sc, upper caudal scute; ud 1-4, urodermals;
una i, una 4, una 5, first, fourth and fifth ural neural arches.
In Pholidolepis the last complete centrum is the first pre-ural in some specimens, but
is normally the first ural (Text-figs 3, 4) : behind this point the notochord was un-
calcified and must have decreased in diameter more sharply than in P. bechei, for
the gap between the hypurals and the ural neural arches seems normally to be
obliterated at the level of the fourth hypural. In Pholidophoropsis both P. caudalis
and P. maculata (Text-fig. 6) show a series of small notochordal calcifications ex-
tending back into the ural region, in the paratype of P. maculata (Text-fig. 6) to the
level of the eighth hypural (nc. u8).
(c) The hypurals and haemal spines. In P. bechei (PI. 3, fig. i, Text-figs i, 2) the
last four haemal spines (hpu 1-4} are broad, long and in contact wtih their neighbours,
and support the foremost caudal fin-rays. The last three haemal spines and the
first hypural each bear a small triangular or rhomboid distal element (v.ra), in-
creasing in size from front to rear. Three to five similar distal bones or cartilages
(presumably homologous with those of Pholidophorus) are present in Acipenser
(Whitehouse 1910, pi. 47, fig. 2; Schmalhausen 1912, pi. 15, fig. 12), Polyodon
210 CAUDAL SKELETON IN LOWER
(Whitehouse 1910, pi. 47, fig. 3), Pteronisculus (Nielsen 1942, fig. 50) and Boreosomus
(Nielsen 1942 : 357) : they represent the radials of the hypochordal lobe of the
fin. There has been considerable argument in the past on the question of the com-
position of the hypurals in teleosts; whether they contain radial elements or not.
In Pholidophorus , Polyodon, Pteronisculus and Acipenser the ventral caudal radials
are very similar in size, shape and number, and in the ontogeny of Acipenser they
resemble those of the adult when they first appear (Schmalhausen 1912). Separate
or partially separate elements in some teleost embryos have been interpreted as
ventral caudal radials (Schmalhausen 1912, Totton 1914), but these do not resemble
the ventral radials in Acipenser and Pholidophorus and are not always present
even in primitive teleost embryos. It seems probable that teleosts (see footnote,
p. 219) and living holosteans have lost the ventral caudal radials and that the
hypurals are not compound structures.
Both in Pholidolepis and Pholidophoropsis the last four haemal spines are en-
larged and support caudal fin-rays, as in P. bechei, and at least in Pholidolepis
(35725> 35562, v.ra, Text-fig. 4A) separate hypochordal radial elements were present
like those of P. bechei.
In P. bechei, Pholidolepis and Pholidophoropsis, as in teleosts, the lower lobe of the
forked caudal fin is supported by two hypurals (hi, h2), the second more slender than
the first. In P. bechei there are ten upper hypurals (Text-fig. 2 A, h 3-12), decreasing
gradually in length and breadth. In Pholidolepis there appear to be only nine upper
hypurals (Text-fig. 46, h 3-11}. In Pholidophoropsis the hypurals are visible only
in P.7582, P. maculata (Text-fig. 6), where there are nine upper hypurals (hj-ii},
one less than in P. bechei.
In all three genera, but especially in P. bechei, the heads of hypurals 4-8 have raised
postero-dorsal processes (p.p.ti) of dense, glossy bone, very like that of the scales and
dermal bones in appearance (PI. 5, fig. i).
(d) The neural arches and neural spines. In Pholidophorus bechei, Pholidolepis and
Pholidophoropsis (Text-figs 1-4, 6) the neural spines of the last three pre-ural centra
decrease in length progressively so that they all end at approximately the same
level, the neural spine of the first pre-ural centrum (npu i) being very short. The
neural arches and spines of these last pre-ural centra (best seen in Text-fig. 6,
Pholidophoropsis maculata, npu i, npu 2} are median unpaired structures, in the
shape of an inverted " Y ". The succeeding neural arches of the ural region (ural
neural arches) are all separate, paired structures, without median neural spines
(Text-fig. 5). These paired ural neural arches are rather complex, variable struc-
tures. There are up to eight pairs in Pholidophorus bechei (I. una 8, r.una 8, Text-
fig. 5) and Pholidophoropsis (una 8, Text-fig. 6), but the number of ural neural
arches is clearly variable since in P.48820 (P. bechei, Text-fig. 56), where the series is
complete and well preserved, there are seven on the right side and eight on the left.
Pholidolepis is not known to have more than seven pairs of ural neural arches
(r.una 7, Text-fig. 46). The detailed structure of the ural neural arches is best seen
in Pholidophorus bechei (Text-fig. 5) but the following description also applies to
Pholidophoropsis and Pholidolepis. The first ural neural arch (1. una i, r.una i,
LIASSIC PHOLIDOPHORID FISHES
una 5
/ I 1
npul
211
ul
nc.pu4
r.una 7
nc.pu4
3mm
TEXT-FIG. 4. Pholidolepis dorsetensis Nybelin. The caudal skeleton as preserved in A,
P.4470Q (see also PL 3, fig. 2); B, P.g^gc. b.f, basal fulcra; ep 1-4, epurals, /./, fringing
fulcra ; h i, h 3, h 4, h n, hypurals i-i i ; hpu i, haemal spine of first pre-ural centrum ;
l.fr, expanded base of lowermost fin-ray of upper caudal lobe ; Luna j-6, ural neural
arches of left side ; nc.pu 4, notochordal calcification (hemicentrum) of fourth pre-ural
vertebra; nc.ui, nc.u 2, notochordal calcifications (hemicentra) of first and second ural
centra; npu i, neural arch of first pre-ural vertebra; sc, ventral caudal scute; r.una 1—7,
ural neural arches of right side ; u i, first ural centrum ; ud, urodermals ; una 1-6, ural
neural arches; v.ra, ventral caudal radial.
2i2 CAUDAL SKELETON IN LOWER
Text-fig. 5; unai, Text-figs i, 3, 4, 6) corresponds fairly closely with the first
pre-ural neural arch (npu i) in shape and size, but is deeper. A notch (n.s.n) is
usually visible on the anterior margin of the first ural neural arch. This notch
corresponds with a notch on the anterior edge of the pre-ural neural arches and must
mark the passage of the segmental spinal nerve, or at least of the dorsal root of the
nerve. Approximately in the centre of the lateral face of the first ural neural arch,
a little above the level of the notch for the spinal nerve, there is usually a small for-
amen (f.v.n, Text-fig. 56, C, also seen in Pholidolepis, Text-fig. 3) which is occasionally
double (Text-fig. 5 A) . Since similar foramina are sometimes present in more poster-
ior ural neural arches (the second in Text-fig. 56, the fifth in Text-fig. 56) these
foramina are probably vascular and without general significance. The second ural
neural arch (Luna 2, r.una 2, Text-fig. 5) is variable in shape, though always shorter
(rostro-caudally) than the first, and is always hollowed antero-laterally to receive the
postero-medial surface of the first ural neural arch. Sometimes (Text-fig. 56, P.
bechei; Text-fig. 6, Pholidophoropsis) the second ural neural arch has an anterior
notch for the spinal nerve. In Pholidolepis the second ural neural arch is usually
produced into a slender postero-dorsal process, curving back above the third arch
(Text-fig. 4 A). The ural neural arches behind the second are even more variable in
shape and are difficult to homologize from one specimen to another. The most
important feature of these more posterior ural neural arches is that they are elon-
gated into slender splints, each arch extending back above its successor and forwards
below its predecessor. An anterior notch for the spinal nerve is occasionally present
on the third ural neural arch (Text-figs 56, 6) but is never found on more posterior
arches. The posterior ural neural arches consist of two regions: the anterior region
is hollowed antero-dorsally, receiving the posterior region of the preceding arch in
this hollow, while the posterior region is rod-like and fits in the hollow of the succeed-
ing arch. The anterior region of the arch is best developed in the arches in the middle
part of the series and extends antero-ventrally around the space occupied in life by
the narrow posterior part of the notochord. The rod-like posterior region of the
arch is also best developed in the middle part of the series, becoming very short in
the last one or two ural neural arches. In Pholidophorus bechei the longest of the
seven or eight ural neural arches is the fourth (Text-fig. 5A) or the fifth (Text-fig. 56).
In Pholidolepis (Text-figs 3, 4) the fourth of the seven ural neural arches is the
longest. In Pholidophoropsis maculata (Text-fig. 6) the fifth to seventh ural neural
arches are equally long. In P. bechei, Pholidolepis and Pholidophoropsis, although the
posterior ural neural arches consist internally of cancellous endochondral bone, their
exposed lateral surfaces are composed of dense, glossy bone resembling in texture
the postero-dorsal processes on the heads of some of the upper hypurals and the
scales and fin-rays (PL 5, fig. i).
(e) The epurals. In teleosts " epural " is the name given to a series of median bones
lying behind the last complete neural spine, and supporting epaxial fin-rays. In
teleosts the epurals do not seem to exceed three in number except in occasional
abnormal individuals. The homologies of the epurals are discussed on p. 220.
In Pholidophorus bechei no specimen shows a complete series of epurals well, but
LIASSIC PHOLIDOPHORID FISHES
213
in P.I54 (PI. 5, fig. i) there are three epurals (ep 1-3), of which the third is the
thickest, above the anterior ural neural arches, and traces of a shorter slender fourth
epural (ep 4} behind these. The stout third epural and short slender fourth epural
of this specimen probably correspond with the two epurals preserved in P. 34822
j Luna 5 l.una 4
> \ \
ep l.una 3 .
/' / Luna 2
B
r.unal
««>8 r.una7 r^6
r.una 5
!-una2 Lunal ,
/ t.v.n
f.vn ,
/
/ ,n.s.n
—r.unal
nuna2 neul
Luna/ 'T6 '-T5
l.una 4
l.una 8— —
2mm
r.una2 n.s.n
TEXT-FIG. 5. Pholidophorus bechei Agassiz. The ural neural arches as preserved in A,
RSM 1888.61.73; B, P.34822; C, P. 48820. ep, epurals; f.v.n, foramina, probably
vascular, in the ural neural arches; l.una 1-8, first — eighth ural neural arches of left side;
nc.ui, dorsal notochordal calcification of first ural centrum; neu, neural canal; n.s.n,
notch for spinal nerve on first ural neural arch; r.una 1-8, first — eighth ural neural arches
of right side.
2I4
CAUDAL SKELETON IN LOWER
(ep, Text-fig. 5B). In Pholidolepis there are four epurals (ep 1-4, Text-figs 3, 4A)
lying above the first ural and first pre-ural neural arches. In Pholidophoropsis
maculata, P-7582 shows five long epurals (ep 1-5, Text-fig. 6), the first four originat-
ing at the tips of the first ural and first pre-ural neural arches, the fifth at the tip of
the fourth ural neural arch.
""08
hn-
nc.uS
nc rpre
-nc.puS
h2
hi
3mm
TEXT-FIG. 6. Pholidophoropsis maculata Nybelin. The caudal skeleton as preserved in
P.7582 (see also PI. 4). ap.sc, anterior process of upper caudal scute; ep 1-5, epurals;
e.sc, enamelled area of upper caudal scute; h i, h 2, h 3, h 4, h n, hypurals i-n; hpu i,
hpu 5, haemal spines of first and fifth pre-ural vertebrae; m.s, dorsal median scale;
nc ? prc, notochordal calcification, probably of poorly preserved precentrum; nc.pu 5,
notochordal calcification (hemicentrum) of fifth pre-ural centrum ; nc.u 5, nc.u 8, noto-
chordal calcifications of fifth and eighth ural centra ; npu i, npu 2, neural arches of
first and second pre-ural vertebrae; una 1-8, first to eighth ural neural arches.
(f) The fin-rays. In Pholidophorus bechei the caudal fin contains twenty-two to
twenty-four principal fin-rays (Text-fig. 7), with the outermost ray in each lobe un-
branched and ten or (normally) eleven branched rays in each lobe. Preceding the
lowermost principal rays there are six or seven unbranched but segmented rays,
grading into fringing fulcra (/./) posteriorly. The uppermost hypaxial fin-ray
is much reduced (r.fr, Text-figs i, 7) ending at a notch on the edge of the uppermost
principal ray at the level of the first fringing fulcra. This reduced uppermost ray is
usually segmented once. The epaxial lobe of the fin is represented only by six or
LIASSIC PHOLIDOPHORID FISHES 215
seven basal fulcra (&./), paired, unsegmented structures, grading posteriorly into
fringing fulcra (/./) inserted on the upper face of the uppermost principal ray. The
seven upper principal rays are very deeply cleft basally, the slender, unsegmented
proximal ends crossing the upper hypurals almost at right angles, and ending at the
level of the third or fourth hypural (Text-fig, i; PL i, PL 5, fig. i). The postero-
dorsal processes (p.p.h) on the heads of the upper hypurals lie against the base of the
upper fin-ray. The fin-rays of the lower lobe of the tail are much less deeply cleft
and only cover the tips of the lower hypurals and the haemal spines (Text-fig, i).
The proximal end of the innermost ray in each lobe of the fin is expanded, as in
Leptolepis coryphaenoides and L. normandica (Nybelin 1963, figs 9, 10) and various
teleosts. The foremost fin-rays in the lower lobe of the fin articulate with the
fourth pre-ural haemal spine, and the rays of the lower lobe are equally distributed
on the last four haemal spines and the first hypural ; the second hypural appears to
carry only a single fin-ray, as it does in most teleosts.
In Pholidolepis there are twenty to twenty-one principal caudal fin-rays, the
outermost in each lobe unbranched, the upper lobe with nine branched rays and the
lower with nine or ten: in this Pholidolepis is closer than Pholidophorus to the
primitive teleostean count of nine branched rays in the upper lobe, eight in the
lower. In Pholidolepis, as in P. bechei, there are about six small rays in front of the
lower principal rays, the foremost articulating with the fourth pre-ural haemal
spine, the seven uppermost hypaxial rays are deeply cleft basally, crossing the upper
hypurals and ending on the third hypural (PL 2 ; Text-fig. 3) and the dorsal margin
of the fin bears fulcra throughout its length. Nybelin (1966 : 392) was unable to
find fulcra on the ventral margin of the tail in Pholidolepis, and some specimens,
including the holotype, were clearly without them, but in 35725 (paratype), 38163
and P.6o67 there are fulcra on the visible parts of the lower edge of the fin. A much
reduced uppermost hypaxial fin-ray (r.fr, Text-fig. 3) is usually present, as in
Pholidophorus bechei, but in Pholidolepis it is unsegmented. The proximal ends of
the innermost fin-rays are expanded, as in P. bechei, but in Pholidolepis the base of
the innermost ray of the upper lobe of the fin, articulating with the third hypural,
is much larger than its neighbours (l.fr, Text-figs 3, 4A), as in Leptolepis dubia
(Text-fig. 10) and Elops (Nybelin 1963, text-fig. 4).
In Pholidophoropsis the number of principal caudal rays is greater than in Pholi-
dophorus bechei : in P. caudalis there are twenty-five, in P. maculata twenty-six to
twenty-seven, both species having five small rays in front of the lower principal
rays. The two uppermost principal rays are normally unbranched, the lowermost
one is often branched. There is no reduced uppermost hypaxial ray such as is
present in P. bechei and Pholidolepis : the unbranched uppermost ray obviously re-
presents this ray in its unreduced condition. The upper hypaxial fin-rays cover the
upper hypurals, as in P. bechei and Pholidolepis. Both margins of the fin carry
fulcra throughout their length.
(g) The squamation. In Pholidophorus bechei the scales are thick, rhombic and
enamelled, and scales of this type cover the caudal endoskeleton and the bases of
the fin-rays completely (Text-fig. 7). The scaling of the upper lobe of the fin is more
2l6
CAUDAL SKELETON IN LOWER
extensive than that of the lower, P. bechei retaining a vestige of the scaled body lobe
of the tail in more primitive actinopterygians. Preceding the basal fulcra (b.f) on
the upper margin of the fin, which are paired structures, there are two or three
median scales (m.s), the anterior one (sc) scute-like, with a long tapering anterior
process (P.35860) . On the lower lobe of the fin the small anterior fin-rays are pre-
ceded by at least one median scale (sc) (38107), probably similar in shape to the
scute-like dorsal median scale.
In Pholidolepis the trunk scales are thin, cycloid, and without enamel (Nybelin
1966 : 391). In front of the basal fulcra on the upper margin of the caudal fin
(b.f, Text-fig. 3) there is a thick, median scale with a slender anterior process (29010,
m.s
.sc
sc
TEXT-FIG. 7. Pholidophorus bechei Agassiz. Restoration of the squamation of the caudal
region and the base of the caudal fin, based on several specimens. The squamation is
drawn as if folded out flat, with the dorsal and ventral median scales shown in surface
view, x 3 approx. b.f, epaxial basal fulcra; /./, fringing fulcra; I. I, course of lateral
line; m.s, median dorsal scale; r.fr, reduced uppermost hypaxial fin-ray; sc, upper and
lower caudal scutes. Arrows indicate the uppermost and lowermost principal fin-rays.
LIASSIC PHOLIDOPHORID FISHES 217
P.6o67 : sc, Text-fig. 3), clearly homologous with the similar scale in Pholidophorus
bechei and in primitive teleosts (Gosline 1965, Patterson, in press). Gosline refers to
this median scute-like structure in teleosts as a fulcral scale, but since it is apparently
homologous neither with the basal fulcra nor the fringing fulcra it will be referred
to here as a caudal scute. Like the urodermals of teleosts (see p. 230) it represents
an almost unmodified relic of the thick, rhombic scales of pholidophorids. In
Pholidolepis the greater part of the caudal scute is covered by thin, cycloid scales,
and as in teleosts, it is without enamel. A similar but smaller caudal scute lies in
front of the lower caudal lobe in Pholidolepis (sc, Text-fig. 4A). Lateral to the post-
erior ural neural arches, in the apex of the wedge-shaped gap between the proximal
part of the uppermost hypaxial fin-ray and the epaxial fulcra, there is in Pholidolepis
a small patch of thick, rhomboid scales. Four of these thick scales are preserved in
P.6o67 (ud 1-4, Text-fig. 3) and P.44707 (ud, PI. 5, fig. 2), three elongated scales lying
in an oblique row, overlapping the uppermost one or two hypaxial fin-rays, and a
fourth more rounded scale above them. No specimen shows more than four scales
clearly, and the preservation is never sufficiently good to show to what extent
these thicker scales were covered by thin, cycloid scales. Like the caudal scutes and
the fin-rays, these thickened scales are without enamel. In shape and position
these scales correspond with the posterior " urodermals " in several of the specimens
figured by Nybelin (1963, Leptolepis normandica, text-fig. 10, Ur j-8\ Allothrissops,
text-fig, n, Ur8; " Thrissops " text-fig. 12, Ur 14-15; Eurycormus, text-figs 13,
15, Ur).
In Pholidophoropsis, as in Pholidolepis, the trunk scales are thin, cycloid, and with-
out enamel. Nybelin (1966 : 415) noted that in P. caudalis " some of the posterior-
most scales are markedly thicker than the body scales ". In both P. caudalis and
P. maculata there is a very thick, conspicuous caudal scute in front of both the upper
and lower lobes of the caudal fin, with a slender anterior process (ap.sc, Text-figs 6, 8)
which evidently passed down into the musculature. The anterior process and the
base of the expanded part of this scale (which is covered by thin, cycloid scales) are
without enamel, but the exposed part is enamelled (e.sc), like the succeeding epaxial
fulcra. This enlarged scale is usually followed by a second median scale, also
enamelled (m.s, Text-fig. 6) and sometimes (Text-fig. 8A) by a third, before the
paired fulcra begin. In Pholidophoropsis these epaxial fulcra are very large and
conspicuous. On the lateral surface of the posterior ural neural arches and the
uppermost hypaxial rays, there is a patch of rhombic, thickened and enamelled
scales. Normally there appear to be eight of these scales in both P. caudalis (Text-
fig. 8B) and P. maculata, arranged in an oblique row of five, partially covering the
bases of the upper hypaxial rays, with three more rounded scales above them. In
the holotype of P. maculata (ud, Text-fig. 8A) there are ten of these scales, an oblique
row of five, an oblique row of four antero-dorsal to these, and a single scale above
this (this specimen also shows a row of three or four thick, enamelled scales immediate-
ly below the thickened dorsal caudal scute, d.s, Text-fig. 8A). In both P. caudalis
and P. maculata the greater part of this patch of thick, rhombic scales is covered by
thin, cycloid scales, only the tips of the most posterior scales being exposed (Text-
fig. 8).
GEOL. l6, 5. 23
218
CAUDAL SKELETON IN LOWER
b.f
ud
TEXT-FIG. 8. Sketches of the base of the upper lobe of the tail in A, 43055, holotype of
Pholidophoropsis maculata Nybelin, with ten urodermals; B, P. 3664^, Pholidophoropsis
caudalis (Woodward), with eight urodermals. The broken lines indicate the posterior
limit of the thin, cycloid scales, b.f, epaxial basal fulcra; d.s, dorsal thickened scales in
P. maculata; f.f, fringing fulcra; ms, median dorsal scales between the caudal scute
and the basal fulcra; sc, caudal scute; ud, urodermals.
III. DISCUSSION
(a) Comparison with chondrosteans , holosteans and teleosts.
In Lower Liassic pholidophorids, despite the advanced, almost teleostean condi-
tion of the skull (Rayner 1948 : 338; Gardiner 1960 : 347) and other such typically
teleostean features as intermuscular bones (Lund 1966), the vertebral column and
caudal skeleton retain many strikingly pre-teleostean features. In the vertebral
column these primitive features include:
i. Formation of the centra entirely by calcifications in the sheath of the uncon-
stricted notochord. Among actinopterygians centra of this type are known only in
the Triassic chondrostean family Pholidopleuridae. In teleosts chordal centra
occur as a transient phase in larvae of primitive forms such as Clupea (Ramanujam
1929) and Salmo (Fran?ois 1966) and in the Upper Jurassic or Lower Cretaceous
Lycoptera, sometimes classed as a teleost, sometimes as a halecostome, chordal
centra appear to have been present in adults (Saito 1936, pi. 4, fig. 5), although the
notochordal calcifications are completely covered by perichordal ossifications.
LIASSIC PHOLIDOPHORID FISHES 219
2. Formation of the centra by opposed, partially or completely separate dorsal
and ventral hemicentra. Similar centra are known only in parts of the vertebral
column of some pholidopleurids, and in the Triassic chondrostean Turseodus
(Schaeffer 1967).
3. The diplospondylous structure of the vertebrae in the middle part of the cau-
dal region. This is a typically holostean feature : no teleost or leptolepid is known
to show diplospondyly of this type, although all the centra are diplospondylous in
young individuals of Ly copter a (Saito 1936 : 9) and in the Upper Cretaceous " eel "
Enchelion (Hay 1903 : 441, pi. 37).
In the caudal skeleton the more important primitive features are:
1. The strong asymmetry of the caudal endoskeleton, with a long, upturned
axis, despite the almost perfect external symmetry of the fin.
2. The absence of centra or notochordal calcifications beyond the first ural centrum
(except for a series of small, irregular calcifications in Pholidophoropsis , Text-fig. 6).
3. The presence of free radials at the tips of the last few haemal spines and the
first hypural.
4. The numerous hypurals (11-12).
5. The presence of four (Pholidophorus bechei, Pholidolepis} or five (Pholido-
phoropsis) epurals.
All these features (except the third, the presence of hypaxial caudal radials, which
do not seem to have been found yet in holosteans) are typical of chondrosteans and
generalized holosteans: none is found in teleosts1. Even in the most primitive
teleosts (including the leptolepids) the caudal skeleton is almost symmetrical (al-
though the truncated axis is upturned the hind edges of the hypurals form an almost
vertical line), there are two (rarely three, Hollister 1936, Greenwood 1967) peri-
chordally ossified ural centra, eight or fewer hypurals and three or fewer epurals.
Teleosts appear to have lost the hypaxial radials1, not incorporated them into the
haemal spines and hypurals. But despite the generally archaic structure of the
caudal endoskeleton, these pholidophorids approach or foreshadow the teleosts in
the presence of only two lower hypurals which support the majority of the principal
rays of the lower caudal lobe (in contrast to amioids (Nybelin 1963, text-figs 17-19)
and Eurycormus (Nybelin 1963, text-figs 13-15)), in the specialization of the ural
neural arches (see below, p. 221), the differentiation of the most posterior scales (both
median p. 217, and lateral p. 229), and in the reduction of the number of principal
caudal fin-rays in the sequence Pholidophoropsis (25-27) - Pholidophorus bechei
(22-24) ~ Pholidolepis (20-21) towards the generalized teleostean arrangement of 19
principal rays with nine branched in the upper lobe, eight in the lower.
In the earliest leptolepids in which the structure of the vertebral column and caudal
skeleton are known (Leptolepis coryphaenoides and L. normandica, Upper Lias,
Rayner 1937, Nybelin 1962, 1963) the vertebrae are perichordally ossified cylinders,
constricting the notochord, there is no trace of diplospondyly and the caudal skeleton
1 Nybelin (pers. commn) has found small ossifications and cartilages at the tips of the last three haemal
spines and the first hypural in adult Recent Flops. These appear to be much reduced ventral caudal
radials, and will be described by Nybelin,
220 CAUDAL SKELETON IN LOWER
has the generalized teleostean arrangement of two ural centra, three epurals, no
hypaxial radials and about eight hypurals whose hind edges are almost vertical
(P. 7622, Leptolepis coryphaenoides , shows six upper hypurals, 37859, L. dubia,
shows seven) . The structure of the caudal skeleton in Lower Liassic pholidophorids
shows that in the pholidophorid/leptolepid transition there was a drastic change in
the mode of formation of the centra and a sharp reduction in the asymmetry of the
caudal endoskeleton. Possible functional explanations of these changes are dis-
cussed below (p. 231).
(b) The homologies of the epurals
Teleostean epurals, primitively three in number, are normally interpreted as
neural spines which have become detached from their neural arches (Gosline 1960,
Nybelin 1963, Monod 1967, Greenwood 1967), but they have also been taken to be
radials, homologous with the pterygiophores of the dorsal fin (Whitehouse 1910,
Goodrich 1930; these authors used the term epural in a different sense from that
defined on p. 212). The presence of four epurals in Pholidophorus bechei and Pholi-
dolepis and five in Pholidophoropsis (which is less closely related to the leptolepids
and teleosts, p. 236) suggests that the three epurals of generalized teleosts are the
remains of a primitively more numerous series. This seems to be confirmed by an
examination of more primitive actinopterygians. In the living chondrosteans
Acipenser (Whitehouse 1910, pi. 47, fig. 2; Schmalhausen 1912, pi. 15, fig. 12) and
Polyodon (Whitehouse 1910, pi. 47, fig. 3) there is a long series of thirty or more rod-
like elements above the posterior neural arches, supporting the epaxial basal fulcra.
These cartilages, which are always interpreted as dorsal caudal radials, do not
correspond in number or position with the neural arches below them. The only
palaeoniscoid in which the caudal skeleton is well known is the Triassic Pteronisculus
(Nielsen 1942, pi. 24, text-fig. 50), in which there are about fifteen similar elements,
also interpreted by Nielsen as dorsal caudal radials, which here have a one-to-one
relation to the underlying neural arches. In the Triassic pholidopleurid Australo-
somus (Nielsen 1949, text-fig. 45) there are five dorsal elements, one-to-one above the
neural arches. In Amia there are three or four dorsal radials (Nybelin 1963, text-
fig. 16; Schmalhausen 1912, pi. 18, fig. 56) and in the more primitive amioid Urocles
there are five (Nybelin 1963, text-fig. 17), in both genera corresponding with the
neural arches. Thus there is clear evidence in actinopterygians of a progressive
reduction in the number of median dorsal elements below the epaxial basal fulcra
(in chondrosteans and most holosteans) or fin-rays (in most teleosts). The epurals
of teleosts must be regarded as members of this series of bones, and the name
" epural " is sufficiently well established, terse and descriptive to apply to the series
in all actinopterygians. There is one-to-one correspondence between the epurals
and the neural arches in all the actinopterygians mentioned except Acipenser and
Polyodon : conditions in these two fishes and the fact that in most actinopterygians
fulcra or fin-rays articulate with the epurals might suggest that the epurals are
dorsal caudal radials, serial homologues of the dorsal pterygiophores, which are
primitively not metameric (Lindsey 1956, Frangois 1959). But the articulation
between the epurals and the epaxial fulcra or fin-rays is very different from the
LIASSIC PHOLIDOPHORID FISHES 221
complex, mobile, muscular joint between dorsal pterygiophores and fin-rays, and
in teleosts epaxial fin-rays often articulate with neural spines anterior to the epurals.
On the other hand, there is good evidence from several different teleosts that the
foremost epural can arise by detachment of a neural spine or can fuse with a neural
arch so that it is indistinguishable from a neural spine (Whitehouse 1910, Norden
1961, Patterson, in press, etc.) : this and the general occurrence, even in palaeoniscoids,
of a one-to-one relationship between the epurals and the neural arches indicate that
the epurals are detached neural spines, serial homologues of the metameric supra-
neurals above the anterior neural arches in chondrosteans, most holosteans and
many generalized teleosts, which are detached neural spines (Goodrich 1930 : 88;
Eaton 1945). If this interpretation is correct, the imperfect correspondence be-
tween the epurals and the neural arches in living chondrosteans must be secondary,
a reasonable assumption in view of the aberrant nature of the skeleton of these
fishes. One is led to the conclusion that the epurals of teleosts are the remains of a
longer series of metameric bones in primitive actinopterygians which are detached
neural spines, serial homologues of the supraneurals developed anteriorly.
(c) Uroneurals and urodermals
On the dorso-lateral surfaces of the ural centra and the first one to four pre-ural
centra of primitive teleosts there is a series of paired, elongate bones, extending back
between the proximal ends of the epaxial fin-rays. Tate Regan (igioa, b) named these
bones " uroneurals " and interpreted them as " neural arches pertaining to posterior
centra which have aborted " (19106 : 533). Nybelin (1963) showed that in Upper
Jurassic teleosts these bones may be numerous and may extend beyond the axial
skeleton on to the surface of the dermal fin-rays, an unlikely position in which to
find endoskeletal neural arches. Nybelin compared the series of bones with the
elongate rhombic scales covering the body lobe of the heterocercal tail in chondro-
stean fishes such as Acipenser, Polyodon, Birgeria and Tarassius, and interpreted them
as scales which have sunk inwards (in phylogeny) and become associated with the
vertebral centra, proposing the name " urodermals " for them. The details of the
structure of the ural neural arches and the caudal squamation in the pholidophorids
described here show that these two interpretations, the endoskeletal " uroneurals "
of Tate Regan and the dermal " urodermals " of Nybelin, are not mutually ex-
clusive. The foremost members of the uroneural/urodermal series, normally applied
to or fused with the ural and pre-ural centra (the only ones present in the great
majority of teleosts), are modified ural neural arches, correctly called uroneurals and
referred to as such in the discussion of post- Jurassic teleosts below. The most
posterior members of the series, present only in a few primitive teleosts and lying
on the uppermost hypaxial fin-rays, are scales, almost unmodified relics of the thick,
rhombic scales of Pholidophorus , and are correctly called urodermals.
(i) The uroneurals.
In Pholidophorus bechei (PL i, PI. 3, fig. i, PL 5, fig. i; Text-figs i, 2, 5), Pholi-
dolepis (PL 2, PL 3, fig. 2; Text-figs 3, 4) and Pholidophoropsis (PL 4; Text-fig. 6)
GEOL. 16, 5. 23§
222 CAUDAL SKELETON IN LOWER
the ural neural arches are paired structures and those behind the first are successively
modified into elongate, rod-like structures, each fitting closely into a hollow on the
antero-dorsal surface of its successor. In Pholidophorus bechei there are seven or
eight pairs of ural neural arches, in Pholidophoropsis maculata there are eight, and in
both species all but the first two pairs are modified, elongate structures. In Pholi-
dolepis only seven pairs of ural neural arches have been seen, all but the first pair
modified. Since these bones are in series with and grade into the pre-ural neural
arches, lie directly over the space occupied in life by the notochord, are thick and
consist internally of cancellous endochondral bone, and in P. bechei are completely
TEXT-FIG. 9. Sketches illustrating variations in the ural neural arches in Leptolepis cory-
phaenoides. In A and B the first ural neural arch is unmodified, in C it is modified into a
uroneural. In A the first uroneural extends to the second pre-ural centrum, in B
to the third, pu 1-3, pre-ural centra; u i, u2, ural centra; una i, una 3, unaj, ural
neural arches 1-7.
covered by thick, enamelled scales, there can be no doubt that they are endoskeletal
neural arches, not dermal scales.
The seven or eight ural neural arches of Lower Liassic pholidophorids may be
compared directly with the uroneurals of the Upper Liassic Leptolepis coryphaenoides
and L. normandica (Text-fig. 9; Nybelin 1963, text-figs 9, 10). In P. 948 (L.
coryphaenoides, Nybelin 1963, text-fig. 9) the first ural neural arch is unmodified, as
in pholidophorids, and there are six modified ural neural arches (una 2-7, Text-fig. 9 ;
Ur 2-7 in Nybelin's figure). Ur 8, the most posterior element labelled in Nybelin's
figure, is probably not a ural neural arch but the remnant of the uppermost hypaxial
fin-ray, already much reduced in Pholidophorus and Pholidolepis (r.fr, Text-figs i,
3, 7). In contrast to Pholidolepis, where the fourth ural neural arch is the longest
and none of the ural neural arches extends forwards beyond the first ural centrum,
in L. coryphaenoides the second to fourth ural neural arches are equally long, the
LIASSIC PHOLIDOPHORID FISHES 223
second extending forwards to the second (Text-fig. gA) or third (32456, Text-fig. gB)
pre-ural centrum, the third to the first or second pre-ural centrum, and the fourth to
the first ural centrum (which in Leptolepis and all teleosts supports the first two
hypurals and is the product of fusion of two centra) . A further variation found in
both L. coryphaenoides (32467, Text-fig. gC) and L. normandica (32583) is that the
first ural neural arch, unmodified in pholidophorids and in most specimens of these
two species, is elongated like its successors, extending forwards to the third pre-ural
centrum. Leptolepis normandica does not seem to differ from L. coryphaenoides
in the structure of the ural neural arches, but some of the specimens identified as
L. coryphaenoides may be L. normandica since the two species are at present distin-
guishable only when the head is well preserved.
In the more advanced Upper Jurassic form Allothrissops (P. 915, P.gija, P.368oc,
P. 7663; Nybelin 1963, text-fig, n, Patterson 1967, text-fig. 3) one can recognize
seven ural neural arches, the first unmodified, the second to seventh all greatly
elongated and sometimes showing fusions (Patterson 1967, text-fig. 3, D 5 +6) or
apparent subdivisions (Nybelin 1963, text-fig, n, Ur 6-7). As in some specimens of
Leptolepis coryphaenoides, the second ural neural arch extends forwards to the
third pre-ural centrum, but in contrast to L. coryphaenoides the third, fourth, and
often the fifth extend to the second pre-ural centrum, the sixth extends to the
first pre-ural centrum and the seventh to the first ural centrum. In the related
Upper Jurassic Thrissops (P. 3684; Nybelin 1963, text-fig. 12) the ural neural
arches are as in Allothrissops except that the second is even more elongate, ex-
tending forwards to the fourth pre-ural centrum, and in Nybelin's figured specimen
there are seven elongate ural neural arches (Ur i-j}.
In the Upper Jurassic Leptolepis dubia (Text-fig. 10; Nybelin 1963, text-fig. 8,
Patterson 1967, text-fig. 6), in which the skull is in many ways more primitive than
in Allothrissops (Patterson 1967, text-figs 2, 4), the condition of the ural neural
arches is more complex. The first five ural neural arches do not differ from those of
Allothrissops and Leptolepis coryphaenoides; the first (una i) is unmodified and the
second to fifth (una 2-5) are greatly elongated, the second extending forwards to the
third pre-ural centrum (pu 3} . Behind the fifth ural neural arch there are three less
elongate bones (una 6-8), the first originating well behind the second ural centrum,
which are inclined in sequence behind one another as are the preceding ural neural
arches, but which lie lateral to the fifth ural neural arch. This arrangement can be
seen in several specimens (37090, 37847, 37859, 37865; Nybelin 1963, text-fig. 8,
Ur 5-7, Patterson 1967, text-fig. 6, D 5-7) and seems to be constant for the species.
In shape and in their mode of articulation with each other (best seen in 37090) these
three posterior bones resemble the posterior ural neural arches of pholidophorids and
Leptolepis coryphaenoides, and like them they end posteriorly medial to the bases of
the epaxial basal fulcra (&./.)• Since these three bones correspond in number and
position with the sixth to eighth ural neural arches in pholidophorids they are clearly
ural neural arches, despite their differentiation from the more anterior arches and
their position lateral to the fifth.
Among known Cretaceous and later teleosts the maximum number of elongate,
strap-shaped uroneurals (ural neural arches) is five, which occurs in some specimens
224
CAUDAL SKELETON IN LOWER
of the Upper Cretaceous genera Xiphactinus, Ichthyodectes and Gillicus (Cavender
1966) : in some specimens of Xiphactinus there are four long uroneurals on one side,
five on the other (Cavender 1966 : 6). These Cretaceous ichthyodectids also show
the maximum forward extension of the uroneurals, which may reach the fourth pre-
ural centrum, as in Thrissops. Among living teleosts the maximum number of
elongate uroneurals is four, found in some specimens of Hiodon (Gosline 1960 : 341).
The specimen of Hiodon alosoides figured by Gosline (BMNH 1892 . 12 . 30 . 555 ; 1960,
una2
unal
npul
\
\
una 4
\ \
una 5
\ "
epl-3
\
una 3
\
\ \
i 1
' i
1 \
\
\
\ ;
_LJ_
una6 P'P'h una 73
b.f
f.f
F
/I
1 /
/I
/ ' /
/I
; J
/ ' /
l.fr
h3
TEXT-FIG. 10. The caudal skeleton of Leptolepis dubia, drawn mainly from P.gay, slightly
restored, b.f, epaxial basal fulcra; c.s, caudal scute; ep 1-3, epurals; /./, fringing
fulcra; h 1-3, hypurals 1-3; hpui, first pre-ural haemal spine; l.fr, expanded base of
lowermost fin-ray of upper caudal lobe; npu i, first pre-ural neural arch; p.p.h, postero-
dorsal processes on heads of upper hypurals ; pu 3, third pre-ural centrum ; u i, first
ural centrum; ud 1-2, urodermals; unai-8, first-eighth ural neural arches.
text-fig. 4) shows a most interesting condition. On the left side of the tail (Text-
fig, n) there are three long uroneurals (l.un 1-3), the first ending anteriorly on the
second pre-ural centrum (pu 2), the second and third on the first pre-ural and first
ural centra respectively. The third uroneural has a small ventral process on the
second ural centrum (u 2) : this process (present on both sides of the specimen)
probably indicates that the third uroneural is a compound structure formed by fusion
of two ural neural arches, almost certainly homologous with the fourth and fifth ural
neural arches of Leptolepis. On the right side of this specimen of Hiodon alosoides
(Text-fig, n) there are four uroneurals, as Gosline (1960 : 341) noted, but the
first of these (r.uni), ending anteriorly on the second pre-ural centrum, is short
LIASSIC PHOLIDOPHORID FISHES
225
and is continuous posteriorly with the small neural arch on the first ural centrum
(the first ural neural arch), a structure which is unmodified on the left side of the
specimen (l.nui), and in all the fishes so far discussed except some individuals of
Leptolepis coryphaenoides and L. normandica (Text-fig. gC). The second uroneural
(r.un 2], the antimere of the first on the left side of the fish and representing the
second ural neural arch, is truncated anteriorly and ends on the first pre-ural centrum,
r.un 2
.un3
po2
TEXT-FIG, n. Hiodon alosoides, caudal skeleton of BMNH 1892.12.30.555, right side
above, left side below, ep, epural; h 1-7, hypurals; hpu i, haemal spine of first pre-ural
vertebra; l.nu i, first ural neural arch of left side; l.un 1-3, uroneurals of left side; npu i,
neural spine of first pre-ural vertebra; pu 2, pu 3, second and third pre-ural centra;
r.un. 1-4, uroneurals of right side; u i, u 2, first and second ural centra.
226 CAUDAL SKELETON IN LOWER
above the tip of the third uroneural (r.un 3). The individual abnormality on the
right side of this specimen of Hiodon alosoides shows beyond question that uroneurals
arise by modification of ural neural arches, and indicates that the morphogenetic
mechanism inducing these modifications may occasionally operate beyond its usual
field (the second and more posterior ural neural arches). The five uroneurals which
Cavender (1966) found in some specimens of the Cretaceous Xiphactinus, Ichthyo-
dectes and Gillicus may be the result of a similar modification of the first ural neural
arch, for Cavender found no neural arch on the first ural centrum in these fishes, and
the first uroneural in the specimen of Ichthyodectes which he figures (text-fig. lA)
is very like the modified first ural neural arch of Hiodon in size and length. This un-
usual plasticity of the ural neural arches in ichthyodectids and Hiodon (which probab-
ly belong to the same teleost lineage, Greenwood et al. 1966 : 360) is interesting in view
of the complete loss of uroneurals in most osteoglossomorph teleosts (Greenwood
1967).
In the primitive living teleosts Elops, Megalops and Tarpon there are three uro-
neurals (Tate Regan 19100, text-fig, i; Hollister 1936, text-figs 14, 16, 19; Nybelin
1963, text-figs 4, 7, Ur 1-3). The first two are elongated bones ending anteriorly
on the second (Elops) or first (Megalops, Tarpon) pre-ural and the first ural centrum
respectively, the third a small splint originating well behind the second ural centrum
and lying below (Megalops, Tarpon) or lateral (Elops) to the tip of the second. In
Elops the anterior end of the first uroneural is forked, the upper limb passing for-
wards to the second pre-ural centrum, the lower ending on the first pre-ural. Tate
Regan (19100) considered this forking to indicate that the first uroneural is a com-
pound bone, and saw a line of junction between the two components in some speci-
mens. Although neither Hollister (1936) nor Nybelin (1963) saw such a line, this is
probably true: in the dussumieriid Jenkinsia the first uroneural corresponds in
position with that of Elops and arises as two bones which later fuse (Hollister
1936 : 279). Exactly similar forking of the first uroneural is seen in other teleosts
(" Clupavus , Patterson 1967, text-fig, n; Nematonotus, Patterson, in press, text-
fig. 25) and probably always indicates that two ural neural arches have fused. Tate
Regan also saw a line of junction in the second uroneural of Elops : if this observation
were confirmed this uroneural would correspond with the compound third uroneural
of normal individuals of Hiodon (Text-fig, n), which it resembles in size and
position, just as the compound first uroneural of Elops corresponds to the first two
uroneurals of normal Hiodon, and the two large uroneurals of Elops would be homo-
logous with the second to fifth ural neural arches of Leptolepis. The small third
uroneural of Elops, Megalops and Tarpon, originating behind the second ural cen-
trum, lying lateral to or behind the tip of the second (= 4th + 5th ural neural
arches) and ending medial to the bases of the fin-rays, has no homologue in Hiodon
but exactly resembles the sixth ural neural arch of Leptolepis dubia (una 6, Text-
fig. 10) and a similarly placed third uroneural in many teleosts (young Albula,
Hollister 1936, text-fig. 23; clupeoids, Hollister 1936, text-figs 43-52, Cavender
1966, text-figs 3, 4, Monod 1967, text-fig. 9, Patterson 19670, text-fig. 8; salmonids,
Schmalhausen 1912, pi. 18, fig. 60, Norden 1961, pis. 14, 15, Gosline 1960, text-figs 5,
12; Argentina, Gosline 1960, text-fig. 10; non-siluroid ostariophysans, Weitzman
LIASSIC PHOLIDOPHORID FISHES
227
1962, text-fig. 15, Gosline 1961, text-fig. iD). Occasionally there is a second small
uroneural, as in the specimen of Salvelinus grayi figured by Gosline (1960, text-fig.
2, UN 4). In this specimen (BMNH 1905.12.8.5) the small fourth uroneural is
comparable to the seventh ural neural arch of Leptolepis dubia (una 7, Text-fig. 10),
but a similar structure has not been found in other individuals of this species, or in
other salmonids, although the caudal skeleton of these fishes has received more
attention than that of any other group (Norden 1961, Vladykov 1962, and many
ealier papers).
In a specimen of Alepocephalus restrains, Gosline (1960, text-fig, i) shows two
small uroneurals (UN 2, 3) comparable with the third and fourth uroneurals in
Salvelinus grayi, but in this specimen (BMNH 1886.8.4.7; Text-fig. 12) I find a
small fourth uroneural (un 4) which is separate only on the left side of the fish, being
fused into the third uroneural on the right side. This individual of Alepocephalus
has three small uroneurals (un 2-4} comparable with the sixth to eighth ural neural
arches in Leptolepis dubia (una 6-8, Text-fig. 10). The first uroneural in Alepo-
un2
un3
epl-2
nul
4mm
TEXT-FIG. 12. Alepocephalus restrains, caudal skeleton of BMNH 1886 .8.4.7. The neural
arch of the first pre-ural centrum is broken off in this specimen, ep 1-2, epurals; h 1-6,
hypurals; hpui, haemal spine of first pre-ural vertebra; nu i, first ural neural arch;
pu 2, second pre-ural centrum; u 2, second ural centrum; un 1-4, uroneurals.
228 CAUDAL SKELETON IN LOWER
cephalus (un i) is very large and appears to consist of four fused ural neural arches,
two ending anteriorly on the second pre-ural centrum (pu 2} , and one ending at the
hind end of both the first pre-ural and the first ural centra. This fish also has a small
unmodified and paired neural arch on the first ural centrum (nu I, the first ural
neural arch), and an indication of the posterior end of the second ural neural arch
in a process on the upper edge of the first uroneural above the hind end of the first
ural centrum. Alepocephalus seems to exhibit the most complete set of uroneurals
among living teleosts, with traces of eight ural neural arches, the first (nu j) un-
modified, the second to fifth much elongated and fused (un i], the sixth to eighth
small and separate (un 2-4} .
Interpretation of the uroneurals of teleosts as modified ural neural arches is support-
ed by Monod's observation (1967) that in elopoids the uroneurals may be preformed
in cartilage. But it is necessary to account for two features of the uroneurals which
have been taken to indicate that they are of dermal origin, the fact that they norm-
ally ossify without cartilage precursors, even in such primitive fishes as Megalops
(Hollister 1939, text-fig. 16, Nybelin 1963 : 514) and Clupea (Ramanujam 1929 : 396),
and the superficial appearance of the uroneurals in adult fishes, where they are usually
easily differentiated from the preceding neural arches by their smooth, dense texture,
suggesting dermal bone (Greenwood 1967). In pholidophorids it has been noted
(p. 212) that the lateral surfaces of the ural neural arches are smooth, dense and
glossy, but this is also true of the postero-dorsal processes on the heads of the upper
hypurals (p. 210). The explanation of these points is probably to be found in the
progressive replacement of endochondral and perichondral bone by membrane bone
which occurs in the evolution of the vertebral column of teleosts. In primitive
teleosts the neural and haemal arches are formed largely by ossification of cartilage,
but in advanced teleosts the amount of cartilage is greatly reduced and the arches
may consist entirely of membrane bone (Fransois 1966 : 319). In Clupea the neural
and haemal arches of the trunk ossify perichondrally and endochondrally, but the
uroneurals ossify as membrane bones at a very early stage (2-2-5 cm-> Ramanujam
1929 : 391). The precocious ossification of the uroneurals in ontogeny (which must
occur for functional reasons) is apparently accompanied by a precocious replacement
of endochondral bone by membrane bone in phylogeny, and it is this different mode
of ossification which accounts for the dense texture of the uroneurals.
The history of the uroneurals in teleosts may be summarized as follows :
1. The uroneurals arose by modification of the second and more posterior members
of the series of seven or eight pairs of ural neural arches present in pholidophorids,
and are therefore primitively six or seven in number. Occasionally the first ural
neural arch is also modified (Leptolepis, Hiodon, ? ichthyodectids) .
2. There are six separate uroneurals in Leptolepis coryphaenoides (Text-fig. 9) and
L. normandica (Lower Jurassic) and six or seven in L. dubia (Text-fig. 10), Allo-
thrissops and Thrissops (Upper Jurassic). In post- Jurassic teleosts the number of
uroneurals is reduced by loss or by fusion between members of the series.
3. The seven uroneurals of Leptolepis dubia are differentiated into an anterior set of
four elongated, strap-like bones (representing the second to fifth ural neural arches)
LIASSIC PHOLIDOPHORID FISHES 229
and a posterior set of three short bones (ural neural arches 6-8) which originate well
behind the second ural centrum and lie lateral to the anterior uroneurals. These two
sets of uroneurals are recognizable in primitive members of all the major basal groups
of teleosts (Elopomorpha, Clupeomorpha, Protacanthopterygii, Ostariophysi)
except the Osteoglossomorpha (ichthyodectids and Hiodon (Text-fig, n)), which
have elongate uroneurals only: this supports the view that the Osteoglossomorpha
are derived from near Thrissops and Allothrissops, in which the uroneurals are still
all of one type.
4. The anterior set of four elongate uroneurals, one of which normally ends
anteriorly on each of the first two pre-ural and the two ural centra, is complete
only in the Cretaceous ichthyodectids (Cavender 1966) among post- Jurassic teleosts.
In Upper Cretaceous " Clupavus " the first and second of the four are fused (Patter-
son 1967, text-fig, n), in Hiodon the third and fourth are fused (Text-fig, n), and
in Elops both the first and second and the third and fourth are fused to produce two
large uroneurals. Similar fusions to those in Elops are probably responsible for
the two large uroneurals of clupeomorph, protacanthopterygian and ostariophysan
fishes, and these are the only uroneurals to persist above the myctophoid level.
5. Fusions between these large anterior uroneurals and centra are common in
teleosts. Usually the fusion is between the first uroneural (itself probably compound)
and a compound centrum formed by fusion of the first ural and pre-ural centra:
this occurs notably in clupeoids, ostariophysans, gonorynchiforms, atherinomorphs
and in many paracanthopterygians and acanthopterygians.
6. A second type of fusion, especially characteristic of many protacanthopterygian
and acanthopterygian groups, is the incorporation of the first ural neural arch, and
usually also of the first pre-ural neural arch, into the first uroneural to produce the
" stegural " of Monod (1967).
7. The posterior set of uroneurals consists primitively of three small, splint-like
bones lying lateral to or behind the tip of the last elongate uroneural and ending
posteriorly medial to the bases of the epaxial fin-rays. These bones represent the
sixth to eighth ural neural arches of pholidophorids and Leptolepis dubia. Except-
ing Alepocephalus and a single specimen of Salvelinus grayi, I know of no post-
Jurassic teleost which has more than one of these small uroneurals. Alepocephalus
(Text-fig. 12) has three, the specimen of Salvelinus grayi has two. A single posterior
uroneural is present in elopoids, clupeoids, many protacanthopterygians and non-
siluroid ostariophysans : whether this bone is compound in origin is as yet unknown.
8. Replacement of endochondral and perichondral bone by membrane bone,
which occurs in the neural and haemal arches during the evolution of teleosts, took
place precociously in the uroneurals, so that they are normally ossified without
cartilage precursors and differ in texture from the preceding neural arches.
(ii) The urodermals
In Pholidophoropsis and Pholidolepis, although the trunk scales have become thin,
cycloid and have lost their enamel, there remains a small patch of thick, rhombic
scales, enamelled in Pholidophoropsis, in the apex of the much reduced body lobe of
230 CAUDAL SKELETON IN LOWER
the caudal fin (PI. 5, fig. 2 ; Text-fig. 8). These scales cover the last few ural neural
arches and parts of the bases of the upper hypaxial fin-rays. In Pholidophoropsis
there are eight to ten of these scales, in Pholidolepis there are four. In Leptolepis
dubia two slender, horizontally elongate bones lie one above the other lateral to
the bases of the upper hypaxial fin-rays (Text-fig. 10, ud 1-2; Nybelin 1963, text-
fig. 8, Ur 8-g; Patterson 1967, text-fig. 6, D 8-9), and two exactly similar bones are
also present in L. coryphaenoides (32463, 32467, P.7622) and L. normandica (32583;
Nybelin 1963, text-fig. 10, Ur 7-8). As Nybelin showed, since these bones are super-
ficial to dermal fin-rays they must be dermal in origin : they are obviously homologous
with the four thickened scales in this position in Pholidolepis, and Nybelin's term
" urodermals " should be used for them. In Leptolepis there is no evidence of the
presence of more than two urodermals. In Allothrissops there is normally a single
urodermal (Nybelin 1963, text-fig, n, Ur 8; Patterson 1967, text-fig. 3, D 8), but
P. 9 170 has two, similar in shape and position to those of Leptolepis. In the " Thris-
sops " specimen figured by Nybelin (1963, text-fig. 12) there are two urodermals
(Ur 14-15], as in Leptolepis: in front of these, below the last elongate uroneurals,
there is a row of five elongate-rhombic bones (Urg-13). These five bones do not
appear to be urodermals (scales) since they are arranged in a pattern which is a
dorso- ventral mirror image of the normal scale pattern on the tail (cf. text-figs. 2, 3,
15, 18 in Nybelin's paper). In Leptolepis dubia and Allothrissops I have figured a
row of small bones in a similar position (Patterson 1967, text-fig. 3, D 9-11, text-
fig. 6, D 10-12), but I now believe that these are postero-dorsally directed knobs on
the upper hypurals, like those in pholidophorids (p.p.h, Text-figs 1-3, 10). The
five bones in Nybelin's " Thrissops " specimen appear too large to be knobs on the
upper hypurals and at present I am unable to interpret them. Apart from this one
specimen, no Jurassic teleost is known to have more than two urodermals.
The history of the urodermals in post- Jurassic teleosts can be described briefly.
The only post- Jurassic teleosts in which urodermals have been figured are the living
Elops (Hollister 1936, text-fig. 14; Nybelin 1963, text-figs 4, 5, Ur 4) and Upper
Cretaceous " Clupavus " (Patterson 1967, text-fig, n, D6) and Nematonotus
(Patterson, in press, text-fig. 25) : in all there is only a single urodermal, lying on
the fin-rays, well clear of the uroneurals. In Elops the single urodermal is slender and
elongate, resembling those of Leptolepis, in " Clupavus " and Nematonotus it is
shorter and more ovoid. A single ovoid urodermal also occurs in the Upper
Cretaceous myctophoid Sardinioides attenuatus and in the living Coregonus and
Osmerus (Nybelin, pers. commn) and Argentina. No doubt a single urodermal was
present in other Cretaceous teleosts, but it will only be visible in exceptionally well
preserved specimens and I have not seen one in a cursory examination of likely
genera. Probably a urodermal occurs in other primitive living teleosts, perhaps
in a reduced form, but again I have not found one in a brief search. In teleosts
urodermals are evidently vestigial structures, retained from pholidophoroid an-
cestors; like other such structures (gular, pectoral and pelvic splints, caudal scutes,
fringing fulcra on the upper caudal lobe, etc.), they are of limited occurrence and
no obvious functional significance.
Differentiation of the scales at the tip of the reduced axial lobe of the tail from the
LIASSIC PHOLIDOPHORID FISHES 231
trunk scales to produce urodermals is not confined to the pholidophoroid/teleost
lineage; it also occurred in amioid holosteans (Nybelin 1963, text-figs 17-20).
(iii) The function of the uroneurals
It is necessary to consider why the ural neural arches should have become so re-
markably modified in the evolution of teleosts. Tate Regan (19100) wrote that the
uroneurals " have taken on the function of strengthening the upturned vertebrae,
thus replacing and inducing the abortion of the posterior centra ". Nybelin (1963)
also found the uroneurals to have a strengthening function since in Jurassic forms
they were best developed in fishes with a slender caudal peduncle and a large, deeply
forked caudal fin. Nybelin's comparison of the uroneurals with the scale rows of the
body lobe of the tail in chondrosteans is important. The scales of the caudal axis
in chondrosteans are separated from those of the trunk by a more or less sharp
oblique line at which the orientation of the scale rows changes from antero-dorsal-
postero-ventral on the trunk to antero-ventral — postero-dorsal on the tail. That
this is a real change in orientation of the scales is shown by the reversed direction of
the overlapping of the scales and of the keels and peg-and-socket joints on the inner
surface of the caudal scales (Schultze 1966 : 255, text-fig. 116). Smith (1956 : 12)
noted that this line is a functional boundary, " a hinge about which bending
moments occur ". The strong fibrous attachments between the scales in each caudal
scale row which Smith (1956) described in sturgeons link the rows into functional
units. Smith considered the role of the caudal scale rows to be primarily protective,
but it seems much more probable that they serve to stiffen the upper lobe of the tail :
this may give the upper lobe less flexibility than the lower, so that the tail will
generate lift even when it is externally symmetrical (Affleck 1950), as it is in Polyodon
and many fossil chondrosteans, or it may serve simply to equalize the flexibility of
the two lobes, since the lower lobe should be basically more rigid than the upper
because of the direct alignment of the lepidotrichia and the supporting haemal
spines. As Smith noted, the functional value of the caudal squamation in chondro-
steans is indicated by the retention of these scales in many chondrosteans which
have lost or greatly reduced the trunk squamation (sturgeons, Polyodon, Carboveles,
Coccolepis, Dorypterus, Birgeria, etc.).
It is well known that the evolution of the tail in actinopterygians is linked with
buoyancy and swimming efficiency (see especially Alexander 1966). The reduction in
ossification and thinning of the scales characteristic of many actinopterygian lineages
together with the possession of a swim-bladder lead to a reduction in specific gravity
and the attainment of neutral buoyancy, which allows a great saving in energy
previously expended in generating lift (Alexander 1966, table i). In the tail the
principal change involved is the gradual reduction of the body lobe of the lift-
generating (epibatic, Affleck 1950) heterocercal tail towards the isobatic homocercal
tail of teleosts. In pholidophorids the body lobe of the tail is greatly reduced and
the fin is externally almost perfectly symmetrical (Text-fig. 7) , but the endoskeleton
and the arrangement of the bases of the fin-rays (Text-figs 1-4) are still strongly
asymmetrical. The primitive stiffeners of the caudal axis, the scales of the body lobe,
have been lost and replaced by two new sets of stiffeners, the ural neural arches (above
232 CAUDAL SKELETON IN LOWER
or lateral to the notochord) and the fin-rays (below the notochord). In chondro-
steans the upper hypaxial fin-rays are short, inserting on the underside of the long
body lobe of the tail. In pholidophorids it appears that as the body lobe has been
reduced the upper hypaxial fin-rays are elongated to retain their insertion, the
long bases of these rays eventually replacing the caudal scales as stiffeners of the
caudal axis. The seven or eight upper hypaxial rays of pholidophorids are very
deeply cleft basally and cross the upper hypurals almost at right angles, ending on
the third or fourth hypural. On the heads of most of the upper hypurals there are
peg-like postero-dorsal processes which fit against the uppermost fin-ray (p.p.h,
Text-figs 1-3) and were presumably bound to the fin-rays by connective tissue, lock-
ing them in position. This arrangement, a bundle of thin, slightly flexible rods
(the bases of the fin-rays) bound to both surfaces of a row of stout rods (the hypurals)
lying at right angles to them, must have been rather rigid. The ural neural arches
of pholidophorids, though considerably modified (Text-fig. 5) and interlocking with
each other to form a semi-rigid rod, were applied to an uncalcified notochord and did
not extend forwards to gain support from the calcified part of the notochord: pro-
bably they were less effective stiffeners than the fin-ray /hypural system. It is im-
portant to note that both sets of stiffeners, the fin-rays and the ural neural arches,
end at about the same level, the second ural segment (second hypural and second ural
neural arch), an oblique plane of weakness which is emphasized by the termination of
the first three pre-ural neural spines and the origin of the epurals in the same plane
(Text-figs i, 3, 4.). This plane of weakness corresponds with the functional boundary
(hinge) at which the scales change their orientation in palaeoniscoids and at which
the caudal squamation ends in such forms as Polyodon (Nybelin 1963, text-fig. 3),
sturgeons (Smith 1956, text-fig, i), Birgeria (Nielsen 1949, text-fig. 77), Coccolepis,
etc.
In teleosts this " hinge " at the base of the upper caudal lobe has disappeared.
There are two well ossified ural centra to which the uroneurals are closely applied
and the uroneurals have extended forwards across the level of the " hinge " to gain
support from the first two or three pre-ural centra (Text-figs 9-12), forming a highly
effective set of stiffeners braced on the vertebral column. The upper principal
fin-rays in Jurassic teleosts (Leptolepis, Allothrissops , Thrissops; Text-fig. 10;
Nybelin 1963, text-figs. 8-12) have deeply cleft bases which cover the upper hypurals,
as in pholidophorids, but the angle between the axes of the fin-rays and the hypurals
is much smaller and the differentiation between the upper and lower principal rays
in the degree of overlap on the hypurals is less : in these early teleosts the uroneurals
can be seen to be replacing the fin-ray /hypural system as the main brace of the upper
lobe of the tail. In Cretaceous and later teleosts the upper and lower fin-rays are
normally symmetrically arranged (either both upper and lower principal fin-rays are
deeply cleft at the base, as in scombrids and carangids, or neither is deeply cleft)
and dorso- ventral symmetry is increased by conversion of the epaxial basal fulcra
into segmented fin-rays (Tate Regan igioa : 357). Even in such a primitive teleost
as Elops the arrangement of the fin-rays shows almost perfect dorso-ventral sym-
metry and the upper principal rays are directly aligned with their supporting hy-
purals (Nybelin 1963, text-fig. 4). The uroneurals here appear to strengthen the
LIASSIC PHOLIDOPHORID FISHES 233
weak supports of the upper caudal lobe (several small hypurals articulating with a
small centrum or with the uncalcified notochord, Nybelin 1963, text-fig, i) so that
the two lobes of the fin will be equally flexible, and the pre-ural neural spines have
increased in length, crossing the line of the " chondrostean hinge " to give added
rigidity and symmetry.
These facts suggest that the tails of pholidophorids and teleosts functioned in
rather different ways. In pholidophorids the body lobe is much reduced, the fin is
externally symmetrical and the chondrostean system of stiffening the upper lobe by
scales is obsolete, but the endoskeleton is still basically chondrostean and there was
an oblique plane of weakness at the level of the second ural neural arch, both sets of
stiffeners, the fin-rays and the ural neural arches, ending at this point, and the
junction between the pre-ural neural spines and the epurals lying in the same plane.
This plane of weakness, indicating a line of flexion, corresponds with the line of
flexion in the scaling of chondrostean tails, and the musculature and mode of opera-
tion of the pholidophorid tail must have been similar to those of chondrosteans, with
a stiff upper lobe swinging about an oblique axis. In teleosts, ossification of the ural
and pre-ural centra and forward extension of the uroneurals have eliminated the
chondrostean line of flexion. The uroneurals equalize the flexibility of the upper
and lower lobes of the fin and the fin-rays lose their stiffening function and soon be-
come symmetrically arranged. The endoskeleton is also almost symmetrical even
in primitive teleosts. These changes are presumably associated with the advantages
of neutral buoyancy, but it is difficult to believe that neutral buoyancy was attained
only at the teleost level — a fish like Pholidolepis which must have had a swim-
bladder, had the scales reduced to the typical teleost form, and swam in sea water
(specific gravity 1-025) was certainly capable of achieving neutral buoyancy. Even
in Pholidophorus, where the scales are still thick, rhombic and enamelled, neutral
buoyancy was surely attainable in view of Alexander's observation (1966 : 145)
that Lepisosteus, with very heavily ossified scales and freshwater habitat, can remain
motionless in mid-water. The advantages which the teleosts had over the pholido-
phorids are probably due not to the sudden acquisition of neutral buoyancy but to
three factors, the advantage in the reduced rate of change of buoyancy with depth
which accrues to a fish with a low specific gravity and a small swimbladder (Alex-
ander 1966 : 148), the increased efficiency in horizontal swimming of a fish in which
both lobes of the tail are equal in area and in flexibility, in which the axis is not
upturned, and in which the tail swings about a vertical rather than an oblique axis
(Affleck 1950), and the greater flexibility and elasticity of a trunk which contains a
well ossified vertebral column and is covered by thin, flexible scales.
Returning to the question posed at the beginning of this section, why should the
ural neural arches have become so remarkably modified in teleosts, I conclude that
both Tate Regan and Nybelin were correct in interpreting the uroneurals as stiffeners,
but that the most remarkable feature of the uroneurals, their extension forwards to
articulate with or fuse with centra well in front of the segments in which they ori-
ginally arose, is a method of eliminating the " chondrostean hinge ", producing a
tail which swings about a vertical axis and is then free to develop internal symmetry.
Tate Regan's opinion that the uroneurals " replace and induce the abortion of the
234 CAUDAL SKELETON IN LOWER
posterior centra " is not strictly correct, for in phylogeny these posterior centra
never existed. The uroneurals developed before the ossification of the centra, and
by their presence made numerous ural centra unnecessary. In amioid holosteans,
where the endoskeleton of the tail remains strongly asymmetrical, uroneurals did not
develop but the " chondrostean hinge " was eliminated by the development of many
ural centra extending to the tip of the notochord (Nybelin 1963, text-figs 16, 17, 19).
Although amioids attained neutral buoyancy, this method of stiffening the caudal
axis has prevented them from developing a fully efficient internally symmetrical
tail.
(d) Definition of the Teleostei
In a discussion of possible taxonomic definitions of the Teleostei (Patterson
1967) I reached the conclusion that the caudal skeleton provides the most satis-
factory characters for limiting the group (see also Tate Regan 1923, Gosline 1965).
Under the influence of Nybelin's interpretation of the uroneurals as dermal structures
(urodermals) , I proposed a provisional definition of the Teleostei based on two
features of caudal structure, single centrum support of the two lower hypurals, and
modification of the primary squamation of the caudal axis into elongate urodermals,
in contact with the vertebral column and overlain by scales. It is necessary to re-
consider these criteria, since although the first remains valid the second is meaning-
less : it is clear that the ural neural arches of pholidophorids, which were in contact
with the notochord (normally uncalcified behind the first ural centrum) and are
covered by scales, are homologous with and directly comparable with the uroneurals
of Leptolepis and teleosts. But the caudal structures of pholidophorids described in
this paper have strengthened my opinion that the caudal skeleton provides the
best and most practicable means of limiting the Teleostei, and that the most logical
level at which to place this limit is between the pholidophorids and the leptolepids.
There are trenchant anatomical differences between the caudal skeletons of pholi-
dophorids and leptolepids (cf. Text-figs 1-6 with Text-figs 9, 10), but the tail in
leptolepids is essentially similar to those of later teleosts. These anatomical differ-
ences between pholidophorids and leptolepids appear to have important functional
significance. The essential change in the tail in the pholidophorid/leptolepid transi-
tion is the elimination of the oblique line of flexion, the " chondrostean hinge ",
at the base of the axial lobe of the tail, by forward extension of the uroneurals across
the level of the hinge to gain support from the perichordally ossified ural and pre-ural
centra. On this basis, a definition of the Teleostei can be framed as follows:
" Actinopterygian fishes in which the vertebral centra are perichordally ossified, the
lower lobe of the caudal fin is primitively supported by two hypurals articulating with
a single centrum, and in which the ural neural arches are modified into elongate
uroneurals, the anterior uroneurals extending forwards on to the pre-ural centra ".
It is worth noting that on this definition there is no evidence from the structure of
the tail that the living teleosts are polyphyletic. The uroneurals of the Elopo-
morpha, Clupeomorpha, Protacanthopterygii and Ostariophysi appear to be based
on the pattern found in Leptolepis dubia, those of the Osteoglossomorpha (Hiodon
and ichthyodectids) on the pattern found in Allothrissops, and both these patterns
LIASSIC PHOLIDOPHORID FISHES 235
can be derived from the ural neural arches of Leptolepis coryphaenoides and pholi-
dophorids. Other primitive teleostean caudal characters such as nineteen principal
caudal rays, two ural centra, seven hypurals, three epurals, etc., occur in basal
members of all the major teleostean groups.
(e) Taxonomy and interrelationships of Lower Liassic Pholidophoridae
Nybelin (1966) has written preliminary diagnoses of the family Pholidophoridae
s. str. and the genera Pholidophorus , Pholidolepis and Pholidophoropsis. Information
on the vertebral column and caudal anatomy of these fishes allows these diagnoses
to be amplified as follows:
Family PHOLIDOPHORIDAE sensu Nybelin (1966)
DIAGNOSIS: See Nybelin (1966 : 425) and add " vertebral centra consisting of
calcifications in the sheath of the notochord, no perichordal centra, notochordal
calcifications primarily in the form of opposed dorsal and ventral hemicentra;
vertebrae diplospondylous in the middle part of the caudal region ; eleven or twelve
hypurals, only two lower hypurals ; free ventral caudal radials at the tips of the last
few haemal spines and the first hypural ; seven or eight pairs of ural neural arches,
those behind the first or second modified into elongated splints resembling the
uroneurals of teleosts; four or five epurals; the seven or eight upper principal
caudal rays elongated proximally, crossing the upper hypurals."
Genus PHOLIDOPHORUS Agassiz
DIAGNOSIS. See Nybelin (1966 : 356) and add " notochord uncalcified behind
the first ural centrum, first and second ural neural arches unmodified, four epurals,
twenty-two to twenty-four principal caudal fin-rays, the uppermost hypaxial fin-ray
reduced."
Genus PHOLIDOLEPIS Nybelin
DIAGNOSIS. See Nybelin (1966 : 387) and add " notochord uncalcified beyond
the second ural centrum, second ural neural arch modified, four epurals, twenty to
twenty-one principal caudal rays, the uppermost hypaxial fin-ray reduced, four
thick, rhombic scales (urodermals) at apex of squamation of upper caudal lobe,
caudal scutes small, urodermals and caudal scutes without enamel, fulcra sometimes
present on lower margin of tail."
Genus PHOLIDOPHOROPSIS Nybelin
DIAGNOSIS. See Nybelin (1966 : 411) and add "notochord calcified in the ural
region, second ural neural arch unmodified, five epurals, twenty-five to twenty-
seven principal caudal fin-rays, uppermost hypaxial fin-ray unreduced, eight to ten
thick, rhombic scales (urodermals) at apex of squamation of upper caudal lobe, caudal
scutes large, urodermals and caudal scutes enamelled."
Nybelin (1966 : 427) has also discussed the interrelationships of Pholidophorus,
Pholidolepis and Pholidophoropsis. Mainly on the structure of the preopercular, he
concluded that Pholidolepis is probably derived from Pholidophorus, from which it
236 CAUDAL SKELETON IN LOWER
differs primarily in thinning of the scales and loss of enamel, and that it possibly leads
on to the leptolepids. Pholidophoropsis he found to belong in a different pholido-
phorid lineage, distinct from the Pholidophorus /Pholidolepis line at least since the
Upper Trias. Thinning of the scales and reduction in enamel in Pholidophoropsis
took place independently, and this genus shows little sign of relationship to the
leptolepids. Nybelin's conclusions are fully borne out by the structure of the caudal
skeleton in these fishes. Of the three genera, Pholidolepis is closest to the leptolepids
and teleosts in the number of caudal fin-rays, the number of urodermals, absence of
enamel on the fin-rays, urodermals and caudal scutes, fusion of the dorsal and
ventral notochordal calcifications into complete rings, modification of the second ural
neural arch and tendency to lose the fringing fulcra on the lower margin of the tail.
Nothing in the structure of the tail of Pholidolepis indicates that it was not derived
from Pholidophorus, and the presence of four epurals and a reduced uppermost
hypaxial fin-ray in the two genera suggests that they are related. Pholidophoropsis,
although it resembles Pholidolepis and teleosts in the cycloid scales and the presence
of urodermals, differs from Pholidolepis and Pholidophorus in the series of noto-
chordal calcifications in the ural region and could not have evolved from Pholido-
phorus because it is more primitive in having five epurals and a higher number of
principal caudal rays.
IV. SUMMARY AND CONCLUSIONS
New anatomical facts and conclusions drawn from them in this paper include the
following.
1. In the Lower Liassic Pholidophoridae Pholidophorus bechei, Pholidolepis and
Pholidophoropsis the notochord was unconstricted and centra were formed only by
opposed dorsal and ventral half-ring calcifications in the sheath of the notochord.
There were no perichordal centra as there" are in teleosts, and in the ural region
the notochord was uncalcified except in Pholidophoropsis. The centra were diplo-
spondylous in the middle part of the caudal region.
2. There are eleven or twelve hypurals in these fishes, three or four more than
are known to occur in teleosts, but as in teleosts there were only two lower hypurals.
3. Ventral caudal radials are present in these pholidophorids at the tips of the last
three haemal spines and the first hypural. Similar elements have not been found in
teleost embryos and teleosts have probably lost the ventral caudal radials, not in-
corporated them in the haemal spines and hypurals.
4. There are four epurals in Pholidophorus bechei and Pholidolepis, five in Pholi-
dophoropsis. In teleosts there are no more than three epurals while in primitive
actinopterygians there are many. The epurals are detached neural spines, serial
homologues of the supraneurals above the anterior vertebrae.
5. The uroneurals of teleosts are endoskeletal structures, derived from the seven or
eight pairs of ural neural arches in pholidophorids, all but the first or second of which
are modified into elongate, interlocking splints resembling teleostean uroneurals.
In pholidophorids and primitive teleosts the first ural neural arch normally resembles
the pre-ural neural arches, but in some individuals of Leptolepis coryphaenoides,
Hiodon and possibly in ichthyodectids it is modified into a uroneural. In Upper
LIASSIC PHOLIDOPHORID FISHES 237
Jurassic Thrissops and Allothrissops and in primitive Osteoglossomorpha (Hiodon
and ichthyodectids) all the uroneurals are elongate. In the Upper Jurassic Lepto-
lepis dubia and in Elopomorpha, Clupeomorpha, Protacanthopterygii and Ostario-
physi the uroneurals are differentiated into an anterior set of four long bones (ural
neural arches 2-5) and a posterior set of three small bones (ural neural arches 6-8).
In post- Jurassic teleosts fusion and loss reduce the number of separate uroneurals.
Alepocephalus retains the most complete set of uroneurals among living teleosts.
6. Although the Lower Liassic pholidophorids could probably achieve neutral
buoyancy, their tails were still functionally heterocercal, with an axial lobe stiffened
by the upper hypaxial fin-rays and the ural neural arches which swung about an
oblique line of flexion at which the modified ural neural arches, the upper hypaxial
fin-rays, the pre-ural neural arches and the epurals ended. This line of flexion
corresponds to the " hinge " in palaeoniscoid tails at which the scale-rows change
their orientation. In teleosts this " hinge " is obliterated, primarily by forward
extension of the uroneurals. Teleostean uroneurals serve to equalize the flexibility
of the upper and lower lobes of the tail so that it functions homocercally, and first
the fin-rays and later the endoskeleton achieve dorso-ventral symmetry.
7. Precocious replacement of perichondral and endochondral bone by membrane
bone accounts for the mode of ossification and " dermal " appearance of the uro-
neurals in teleosts.
8. In Pholidophorus bechei the caudal skeleton is covered by thick, rhombic
enamelled scales. In Pholidolepis and Pholidophoropsis the trunk scales have lost
their enamel and become thin and cycloid, but a patch of thick, rhombic scales
persists at the apex of the reduced body lobe of the tail. One or two of these scales
persist on the upper hypaxial fin-rays in a few primitive teleosts as urodermals.
In Jurassic teleosts (Leptolepis, Allothrissops) there are one or two urodermals, in
post- Jurassic teleosts no more than one is known. Elops, Coregonus, Osmerus, and
Argentina are the only living teleosts known to retain a urodermal.
9. A definition of the Teleostei is proposed based on the single centrum support
of the lower hypurals and the forward extension of the uroneurals on to the pre-ural
centra. This definition includes the leptolepids in the Teleostei.
10. Nybelin's account of the interrelationships of the Lower Liassic pholidophorids
is confirmed by caudal structure. Of the three genera dealt with here, Pholidolepis
is closest to the teleosts.
V. REFERENCES
AFFLECK, R. J. 1950. Some points in the function, development and evolution of the tail in
fishes. Proc. zool. Soc. Lond., 1950 : 349-368, 10 figs.
ALEXANDER, R. McN. 1966. Physical aspects of swimbladder function. Biol. Rev., Cam-
bridge, 41 : 147-176, 5 figs.
CAVENDER, T. 1966. The caudal skeleton of the Cretaceous teleosts Xiphactinus, Ichthyo-
dectes, and Gillicus, and its bearing on their relationship with Chirocentrus. Occ. Pap.
Mus. Zool. Univ. Mich., Ann Arbor, 650 : 1-15, i pi.
EATON, T. H. 1945. Skeletal supports of the median fins of fishes. /. Morph., Philadelphia,
76 : 193-212, 5 figs.
FRANCOIS, Y. 1959. La nageoire dorsale, anatomic comparee et Evolution. Annee Biol.,
Paris, 35 : 81-113, 18 figs.
238 CAUDAL SKELETON IN LOWER
FRANCOIS Y. 1966. Structure et developpement de la vertebre de Salmo et des t61eosteens.
Archs. Zool. exp. gen., Paris, 107 : 287-328, 2 pis.
GARDINER, B. G. 1960. A revision of certain actinopterygian and coelacanth fishes, chiefly
from the Lower Lias. Bull. Br. Mus. nat. Hist. (Geol.), London, 4 : 239-384, pis. 36-43.
GOODRICH, E. S. 1930. Studies on the structure and development of vertebrates, 837 pp., 754 figs.
London, Macmillan.
GOSLINE, W. A. 1960. Contributions toward a classification of modern isospondylous fishes.
Bull. Br. Mus. nat. Hist. (Zool.), London, 6 : 325-365, 15 figs.
— 1961. Some osteological features of modern lower teleostean fishes. Smithson. Misc.
Coll., Washington, 142, 3 : 1-42, 8 figs.
— 1965. Teleostean Phylogeny. Copeia, Ann Arbor, 1965 : 186-194, i fig.
GREENWOOD, P. H. 1967. The caudal fin skeleton in osteoglossoid fishes. Ann. Mag. nat.
Hist., London (13) 9 : 581-597, 12 figs.
GREENWOOD, P. H., ROSEN, D. E., WEITZMAN, S. H., & MYERS, G. S. 1966. Phyletic studies
of teleostean fishes, with a provisional classification of living forms. Bull. Am. Mus. nat.
Hist., New York, 131 : 339-456, pis. 21-23.
HAY, O. P. 1903. On a collection of Upper Cretaceous fishes from Mount Lebanon, Syria,
with descriptions of four new genera and nineteen new species. Bull. Am. Mus. nat. Hist.,
New York, 19 : 394-452, pis. 24-37.
HOLLISTER, G. 1936. Caudal skeleton of Bermuda shallow water fishes. I. Order
Isospondyli: Elopidae, Megalopidae, Albulidae, Clupeidae, Dussumieriidae, Engraulidae.
Zoologica, N.Y., 21 : 257-290, 53 figs.
— 1937. Caudal skeleton of Bermuda shallow water fishes. III. Order Iniomi: Synodon-
tidae. Zoologica, N.Y., 22 : 385-399, 18 figs.
— *939- Young Megalops cyprinoides from Batavia, Dutch East Indies, including a study of
the caudal skeleton and a comparison with the Atlantic species, Tarpon atlanticus. Zoolo-
gica, N.Y., 24 : 449-475, 21 figs.
LINDSEY, C. C. 1956. Evolution of Meristic Relations in the Dorsal and Anal fins of Teleost
Fishes. Trans. R. Soc. Can., Ottawa (5) 49 : 35-49, 2 figs.
LUND, R. 1966. Intermuscular Bones in Pholidophorus bechei from the Lower Lias of England.
Science, N.Y., 152 : 348-349, 2 figs.
MONOD, T. 1967. Le complexe urophore des Teleosteens: typologie et evolution (note
preliminaire) . Collogues int. Cent. natn. Rech. scient., Paris, 163 : 111—131, 16 figs.
NIELSEN, E. 1942. Studies on Triassic fishes from East Greenland. I. Glaucolepis and Bor-
eosomus. Meddr Gr0nland, K0benhavn, 138 : 1—403, 30 pis.
— 1949. Studies on Triassic fishes from East Greenland. II. Australosomus and Birgeria.
Meddr Gr0nland, Kobenhavn, 146 : 1-309, 20 pis.
NORDEN, C. R. 1961. Comparative osteology of representative Salmonid Fishes, with parti-
cular reference to the Grayling (Thymallus arcticus) and its Phylogeny. /. Fish. Res.
Bd. Can., Ottawa, 18 : 679-791, 16 pis.
NYBELIN, O. 1962. Preliminary note on two species previously named Leptolepis bronni
Agassiz. Ark. Zool., Uppsala (2) 15 : 303-306, i fig.
— 1963. Zur Morphologic und Terminologie des Schwanzskelettes der Actinopterygier.
Ark. Zool., Uppsala (2) 15 : 485-516, 22 figs.
— 1966. On certain Triassic and Liassic representatives of the family Pholidophoridae s.str.
Bull. Br. Mus. nat. Hist. (Geol.), London, 11 : 351-432, 15 pis.
PATTERSON, C. 1967. Are the teleosts a polyphyletic group? Collogues int. Cent. natn.
Rech. scient., Paris, 163 : 93-109, n figs.
— in press. The caudal skeleton and fin in Mesozoic acanthopterygian fishes. Bull. Br.
Mus. nat. Hist. (Geol.), London, 17.
RAMANUJAM, S. G. M. 1929. The study of the development of the vertebral column in teleosts,
as shown in the life-history of the herring. Proc. zool. Soc. Lond., 1929 : 365-414, 28 figs.
RAYNER, D. H. 1937. On Leptolepis bronni Agassiz. Ann. Mag. nat. Hist., London (10) 19 :
46-74, 14 figs.
LIASSIC PHOLIDOPHORID FISHES 239
RAYNER, D. H. 1948. The structure of certain Jurassic Holostean fishes, with special reference
their to neurocrania. Phil. Trans. R. Soc., London (B) 233 : 287-345, pis. 19-22.
REGAN, C. TATE igioa. The caudal fin of the Elopidae and of some other teleostean fishes.
Ann. Mag. nat. Hist., London (8) 5 : 354-358, 2 figs.
igiofr. On the caudal fin of the Clupeidae, and on the Teleostean Urostyle. Ann. Mag.
nat. Hist., London (8) 5 : 531-533, 2 figs.
1923. The skeleton of Lepidosteus, with remarks on the origin and evolution of the lower
neopterygian fishes. Proc. zool. Soc. Lond., 1923 : 445-461, 8 figs.
SAITO, K. 1936. Mesozoic Leptolepid Fishes from Jehol and Chientao, Manchuria. Rep.
scient. Exped. Manchoukuo, Tokyo, 2, 3 : 1-23, 5 pis.
SCHAEFFER, B. 1967. Osteichthyan vertebrae. J.Linn. Sec. (Zool.), London, 47: 185-195, i pi.
SCHMALHAUSEN, J. J. 1912. Zur Morphologie der unpaaren Flossen. I. Die Entwicklung
des Skelettes und der Muskulatur der unpaaren Flossen der Fische. Z.wiss. Zool., Leipzig,
100 : 509-587, pis. 45-48.
SCHULTZE, H. P. 1966. Morphologische und histologische Untersuchungen an Schuppen
mesozoischer Actinopterygier (Ubergang von Ganoid- zu Rundschuppen). Neues Jb.
Geol. Palaont. Abh., Stuttgart, 126 : 232-314, pis. 49-53.
SMITH, I. C. 1956. The structure of the skin and dermal scales in the tail of Acipenser
ruthenus L. Trans. R. Soc. Edinb., 83 : 1-14, 3 pis.
STENSIO, E. A. 1932. Triassic fishes from East Greenland collected by the Danish expeditions
in 1929-1931. Meddr Gronland, K0benhavn, 83, 3 : 1-305, 39 pis.
TOTTON, A. K. 1914. The Structure and Development of the Caudal Skeleton of the Tele-
ostean Fish, Pleuragramma antarcticum. Proc. zool. Soc. Lond., 1914 : 251-261, 2 pis.
VLADYKOV, V. D. 1962. Osteological studies on Pacific salmon of the Genus Oncorhynchus .
Bull. Fish. Res. Bd. Can., Ottawa, 136 : 1-172, 89 figs.
WEITZMAN, S. H. 1962. The osteology of Brycon meeki, a generalized characid fish, with an
osteological definition of the family. Stanford ichthyol. Bull., Palo Alto, 8 : 1-77, 21 figs.
WHITEHOUSE, R. H. 1910. The Caudal Fin of the Teleostomi. Proc. zool. Soc. Lond.,
1910 : 590-627, pis. 47-50.
ADDENDUM
While this paper was in press R. Lund (1967, An analysis of the propulsive mechanisms of
fishes, with reference to some fossil actinopterygians. Ann. Carneg. Mus., Pittsburgh, 39:
195-218, 12 figs.) published a discussion of the actinopterygian tail, including photographs of
excellent caudal skeletons of several Jurassic genera. On questions dealt with in the present
paper, the structure and nomenclature of the teleostean caudal skeleton, Lund reaches radically
different conclusions from my own. Some of Lund's arguments, such as his identification of the
uroneurals as intermuscular bones, are answered above, and the only points which will be
mentioned here concern the nomenclature of the teleost tail. Lund rejects Nybelin's characteri-
sation of the boundary between the ural and pre-ural regions as the point at which the caudal
vessels bifurcate, writing "this point varies greatly in the teleosts" and is "modified by function".
He defines hypurals as all haemal spines supporting caudal fin-rays and ural centra as all centra
supporting such spines — "haemal spines that support fin-rays are ipso facto specialized . . .
it is necessary to give these specialized haemal spines a collective name". Lund gives no
evidence of variation in the point of bifurcation of the caudal vessels: my own experience and
that of workers who have examined large series of teleost caudal skeletons (Goslind 1965:
191 ; Monod 1967: 113) is that this point is constant. And Nybelin's terminology does provide a
collective name, "pre-ural haemal spines", for haemal spines supporting caudal fin-rays. The
number of pre-ural haemal spines supporting fin-rays must be specified in each case simply
because it varies intraspecifically (e.g. Hollister 1937, n§s- 4~6; Weitzman 1962: 39).
PLATE i
Pholidophorus bechei Agassiz. Posterior part of vertebral column and base of caudal
fin of 19010 (see also Text-fig, i). X5'5.
Bull. Br. Mus. nat. Hist. (Geol.) 16, 5.
PLATE i
GEOL. l6, 5.
PLATE 2
Pholidolepis dorsetensis Nybelin. Posterior part of vertebral column and base of caudal
fin of P. 6067 (see also Text-fig. 3). xj.
Bull. Br. Mus. nat. Hist. (Geol.) 16, 5.
PLATE 2
» ».,
GEOL. 16, 5.
*•
PLATE 3
FIG. i. Pholidophorus bechei Agassiz. Caudal skeleton of RSM 1888.61.73 (see also
Text-fig. 2 A). X7-
FIG. 2. Pholidolepis dorsetensis Nybelin. Caudal skeleton of P.^jog (see also Text-fig.
4A). x 10.
Bull. Br. Mus. nat. Hist. (Geol.) 16, 5
PLATE 3
r .''.-& ,sT' 'Jr*>
PLATE 4
Pholidophoropsis tnaculata Nybelin. Posterior part of vertebral column and caudal
skeleton of P-7582 (see also Text-fig. 6). X5'5-
Bull. Br. Mus. nat. Hist. (Geol.) 16, 5
PLATE 4
PLATE 5
FIG. i. Pholidophorus bechei Agassiz. Base of upper caudal lobe of P. 154, showing the
epurals (ep 1-4), the second to fifth ural neural arches and the heads of the upper hypurals.
X25.
FIG. 2. Pholidolepis dorsetensis Nybelin. Base of the upper hypaxial fin-rays of P. 44707,
showing three urodermals (ud}\ the fourth urodermal is only preserved in impression in this
specimen. X 25.
Bull. Br. Mus. not. Hist. (Geol) 16, 5
PLATE 5
PRINTED IN GREAT BRITAIN
BY ADLARD & SON LIMITED
BARTHOLOMEW PRESS, DORKING
\vl .
THE SUBPHYLUM CALCICHORDATA
(JEFFERIES 1967)
PRIMITIVE FOSSIL CHORDATES
WITH ECHINODERM AFFINITIES
R. P. S. JEFFERIES
BULLETIN OF
THE BRITISH MUSEUM (NATURAL HISTORY)
GEOLOGY Vol. 16 No. 6
LONDON: 1968
THE SUBPHYLUM CALCICHORDATA
I SJULI9,
(JEFFERIES 1967)
PRIMITIVE FOSSIL CHORD ATE S WITH
ECHINODERM AFFINITIES
BY
RICHARD PETER SPENCER JEFFERIES
•v
-4
Pp. 241-339; 10 plates; 27 text-figures
BULLETIN OF
THE BRITISH MUSEUM (NATURAL HISTORY)
GEOLOGY Vol. 16 No. 6
LONDON: 1968
THE BULLETIN OF THE BRITISH MUSEUM
(NATURAL HISTORY), instituted in 1949, is
issued in five series corresponding to the Departments
of the Museum, and an Historical series.
Parts will appear at irregular intervals as they become
ready. Volumes will contain about three or four
hundred pages, and will not necessarily be completed
within one calendar year.
In 1965 a separate supplementary series of longer
papers was instituted, numbered serially for each
Department.
This paper is Vol. 16, No. 6 of the Geological
(Palaeontological) series. The abbreviated titles of
periodicals cited follow those of the World List of
Scientific Periodicals.
World List abbreviation
Bull. Br. Mus. nat. Hist. (Geol.).
Trustees of the British Museum (Natural History) 1968
TRUSTEES OF
THE BRITISH MUSEUM (NATURAL HISTORY)
Issued 2 July, 1968 Price £3
THE SUBPHYLUM CALCICHORDATA
(JEFFERIES 1967)
PRIMITIVE FOSSIL CHORDATES WITH
ECHINODERM AFFINITIES
By RICHARD PETER SPENCER JEFFERIES
CONTENTS
Page
I. INTRODUCTION ......... 245
II. ACKNOWLEDGMENTS ........ 247
III. MORPHOLOGY .......... 247
a. Cothurnocystis elizae Bather ...... 247
Systematic position . . . . . . . 247
Occurrence ......... 247
Material ......... 247
General shape and plate nomenclature .... 248
Thecal openings ........ 248
The chambers of the theca ...... 255
The integuments and mode of feeding .... 258
The stem ......... 259
The brain ......... 264
Ontogeny ......... 264
Posture and movement ....... 265
b. Cothurnocystis curvata Bather ...... 265
Systematic position ....... 265
Occurrence ......... 265
Material ......... 265
General shape and plate nomenclature .... 266
Thecal openings ........ 266
The chambers of the theca . . . . . . 271
The integuments . . . . . . . .273
The stem ......... 275
The brain ......... 276
Posture and movement ....... 276
c. Mitrocy stella incipiens (Barrande) miloni Chauvel . . 277
Systematic position . . . . . . . 277
Occurrence ......... 277
Material ......... 277
General shape and plate nomenclature .... 277
Thecal openings . . . . . . . . 282
The chambers of the theca . . . . . . 283
The stem ......... 289
The brain and cranial nerves . . . . . . 295
Posture, feeding and movement ..... 309
GEOL. 16, 6. 25
244 PRIMITIVE FOSSIL CHORDATES
d. Mitrocystites mitra Barrande . . . . . 310
Systematic position . . . . . . . 310
Occurrence ......... 310
Material ......... 310
General shape and plate nomenclature . . . . 310
Thecal openings . . . . . . . 311
The chambers of the theca . . . . . . 314
The stem 317
The brain and cranial nerves . . . . . . 319
Posture feeding and movement ..... 322
IV. DISCUSSION .......... 323
a. Cornutes and mitrates ....... 323
b. Stylophora, echinoderms, hemichordates and chordates . 327
V. CONCLUSIONS .......... 333
a. Phyletic and systematic position . . . . . 333
b. Thecal openings ........ 333
c. Thecal chambers ........ 334
d. The stem 334
e. The brain and cranial nerves . . . . . . 335
f. Posture and habits ........ 336
g. Definition of subphylum Calcichordata (Jefferies 1967)
= class Stylophora (Gill & Caster 1960) .... 336
VI. REFERENCES 336
SYNOPSIS
The orders Cornuta (Jaekel 1900) and Mitrata (Jaekel 1918), which constitute the class
Stylophora (Gill & Caster, 1960) (Cambrian to Devonian) and which are customarily placed
in the Echinodermata, are transferred to the Chordata as the Subphylum Calcichordata
(Jefferies 1967). With Gislen (1930), the Calcichordata are regarded as ancestral to the
Urochordata, Cephalochordata and Craniata.
The cornutes Cothurnocystis elizae Bather and C. curvata Bather had external branchial slits
in the left, dorsal part of the theca that were mechanically adapted as outlet valves. The
mouth was near the anterior end of the theca. The anus, situated left of the stem, was external
in C. elizae but opened into the most median gill slits in C. curvata. Anterior and posterior
coeloms, pharynx and buccal cavity can be recognized in the theca. The stem, which is homo-
logous with both the stem of a crinoid and the tail of a fish, had an anterior part for lateral
flexion, a posterior part adapted for upwards flexion and a medial rigid part containing a ventral
massive element, the stylocone. In the posterior stem evidence indicates the presence of
segmental muscle blocks, a median chambered organ or notochord and probable paired seg-
mental blood vessels. The brain or aboral nerve centre was at the anterior end of the stem.
The mitrates Mitrocystella incipiens (Barrande) miloni Chauvel and Mitrocystites mitra
Barrande had paired, posterior gill openings and presumed, paired, internal gill slits. The
mouth was at the anterior end of the body and pointed somewhat leftwards, particularly in
juvenile M. mitra, like the mouth of larval amphioxus. Anterior and posterior coeloms, left
and right pharyngeal chambers, buccal cavity and paired posterior atria can be recognized
in the theca. The rectum opened into the left atrium as in a living tunicate tadpole. Left
gill slits probably preceded right gill slits in ontogeny as in amphioxus. The stem, as in cornutes,
had anterior, medial and posterior parts. The anterior part was probably adapted to lateral
flexion, the medial part contained a massive dorsal element (styloid), and the posterior part
was adapted for flexing downwards. In the posterior stem, evidence indicates the presence of
segmental muscle blocks, notochord, dorsal nerve cord, paired segmental ganglia and a compli-
cated vascular system. The brain was at the anterior end of the stem and was fish-like in
WITH ECHINODERM AFFINITIES 245
character with optic, hypophyseal, medullary and olfactory parts. The cranial nerves were
complicated and included homologues of the trigeminal complex and trigemino-profundus
ganglia and of the olfactory, optic and lateralis complexes of fish.
The extant chordate subphyla probably derived from a primitive, probably Upper Cambrian,
mitrate that became free swimming.
The following homologies are suggested between chordates and crinoids: notochord =
chambered organ; dorsal nerve cord = peduncular nerve; longitudinal vessel broadly =
haemal strand; brain = aboral nerve centre; cranial nerves broadly = aboral nerves to theca.
Ubaghs' interpretation of the stem of Stylophora (19616) is rejected as also is the classical
theory of vertebrate head segmentation. Lindstrom's (1949) interpretation of the cranial
nerves of cephalaspids is adopted as the most reasonable yet proposed.
I. INTRODUCTION
THE subjects of this paper are certain bizarre fossils, conventionally regarded as
echinoderms, belonging to the orders Cornuta Jaekel 1900 and Mitrata Jaekel 1918.
The conclusion is reached, with Gislen (1930), that, while having definite echinoderm
affinities, they are better placed in the Chordata, and are the ancestors of other
Chordata, including tunicates, Amphioxus and the vertebrates.
The Cornuta and Mitrata are conventionally regarded as members of Jaekel's
Class Carpoidea 1900. This is usually defined as including the orders Cornuta,
Mitrata, Soluta, Cincta and Digitata (e.g. Gill & Caster 1960 : n). The extent to
which the Carpoidea are a natural group is doubtful. It is certain, however, as
shown below, that Cornuta and Mitrata are closely allied to each other. They were
placed by Gill & Caster (1960 : n) in the distinct Superorder Stylophora, here
regarded as a class.
A relationship between echinoderms, hemichordates and chordates is widely
accepted (p. 327). The suggestion that Cornuta and Mitrata are in fact chordates,
and ancestral to other chordates, is therefore inherently plausible. It was mentioned
in passing by Matsumoto (1929 : 27) and argued in detail, and with great erudition,
by Gislen (1930). Gislen's views were mentioned favourably by Gregory (1935 :
280; 1936 : 321; 1946 : 358), Caster (1952 : 37), and Caster & Eaton (1956). They
have not been widely accepted, however, mainly because Gislen's argument was
based on embryology rather than fossils, and his reconstruction of the soft parts
of cornutes and mitrates was little more than guesswork. Berrill (1955 : 5) dis-
missed Gislen's hypothesis in a paragraph. Marcus (1958 : 50), however, expressed
the view that " Future evidence of the origin of the Chordata from the Carpoidea
would by no means be surprising."
I agree with Gislen's broad results and with some of his major anatomical sug-
gestions such as the position of the mouth in cornutes and mitrates and of gill slits
in cornutes, the homology of carpoid stem and fish's tail, and the homology of some
of the asymmetries of larval Amphioxus with those of mitrates and cornutes. Most
of Gislen's detailed arguments, however, seem to be incorrect.
Other works dealing with the morphology of mitrates and cornutes generally
agree on details but flatly disagree on essentials. Among the most important are
Jaekel (1900; 1918), Bather (1913; 1928), Chauvel (1941) and Ubaghs (19610;
19616; 1963). Chauvel's reconstruction of the nervous system of Mitrocystella is
246 PRIMITIVE FOSSIL CHORDATES
a tour de force and Ubaghs' observations on the details of stem structure are also
highly important, though his conclusions are not acceptable.
The present work takes the form of a detailed morphological study of the cornutes
Cothurnocystis elizae Bather and C. curvata Bather, and the mitrates Mitrocystella
incipiens (Barrande) miloni Chauvel and Mitrocystites mitra Barrande. These forms
were chosen because they are reasonably large (theca about 3 cm. across), well
represented in the British Museum (Natural History) collections and preserved
largely as hollow moulds, with the skeletal calcite dissolved away. This allows
the internal mould to be examined direct and the form of the skeleton to be obtained
by means of latex and dental rubber casts. The reconstructions, based on obser-
vations of as many specimens as possible, were drawn in several projections simul-
taneously on a drawing board. Supplementary observations were made on
Ceratocystis perneri Jaekel, Phyllocystis blayaci Thoral, P. crassimarginata Thoral,
Chinianocarpos thorali Ubaghs, Lagynocystis pyramidalis (Barrande) and Peltocystis
cornuta Thoral.
In reconstructing the soft parts, a functional explanation has been sought for
as many features as possible. It was assumed that the soft parts of the four species
mainly studied were fundamentally the same. The fossils have been interpreted
by analogy first with crinoids, and secondly with tunicate larvae and fish.
The results flatly contradict the idea of a completely segmented vertebrate
ancestor with mandibular and premandibular gill slits which is so firmly embedded
in classical vertebrate anatomy (e.g. Goodrich 1918) but for which the evidence
is, in fact, very weak (Kingsbury 1926). They agree somewhat better with the
views of students of tunicates such as Berrill (1955) and Garstang (1928), except
that there is no evidence of neoteny. They also agree better with the account of
cephalaspid cranial anatomy given by Lindstrom (1949) than with that of Allis
(1931), Wangsjo (1952) or Stensio (1927; 1958). Wangsjo's interpretations are
preferable in many respects to Stensio's but Lindstrom's seem more reasonable
than either.
As regards nomenclature, the terms anterior, posterior, dorsal and ventral, right
and left are used as for a fish. The plate nomenclature is a much modified version
of that of Jaekel (1900). The nomenclature of Caster (1952) could not be used,
since a scheme was needed that was applicable to both cornutes and mitrates and
which was not too dependent on the correct homology of plates. The following
notation is employed: C — a central dorsal plate of the theca, D = a dorsal plate
of the anterior stem, M = a marginal plate, S = a ventral spike, V — ventral plate
of theca, VS = ventral plate of stem, suffix A = anterior, suffix D = dorsal, suffix
L — left, suffix R, = right, suffix y — ventral, suffix (0) x, 2, 3 e^c. indicates position
in sequence counting from anterior end of stem.
A brief account of the work described in the present paper has already been
published (Jefferies 1967), and in that work the name Calcichordata was used for
the first time. Since writing that brief account I have changed' my mind on some
details. Thus the median line nerves of cornutes cannot represent the optic nerves
(n3) of mitrates since they pass ventral to the gut. They may possibly correspond
to the nerves n0 of mitrates. Again, the peripheral canals of M. incipiens miloni
WITH ECHINODERM AFFINITIES 247
probably did not extend forwards to open in the olfactory openings. Consequently
the fibres of the olfactory nerves did not travel anteriorly in the peripheral canals, and
did not have to leave these to reach the telencephalon. The reconstruction of the
anterior parts of the nerves n2 of M. mitra has been altered in some respects. Further
it no longer seems likely, though it is still possible, that the Cephalochordata derived
from a different group of mitrates to the Urochordata and Craniata. The probable
position of the oesophagus of M. i. miloni and the probable ontogenetic origin of
the posterior coelom of M. i. miloni and M. mitra were not discussed in the earlier
paper. None of these are very important points and they do not affect the funda-
mental thesis here advanced.
II. ACKNOWLEDGMENTS
The author gratefully acknowledges the help of numerous colleagues. Dr. W. T.
Dean initiated the investigation by finding a mitrate from Shropshire that he
discussed with the author. Mr. H. G. Owen and Mr. A. E. Rixon have been very
helpful in technical matters. Drs. Horny and Zazvorka of Prague, M. Mattei of
Montpellier, Prof. Milon of Rennes, Dr. B. Kummel of Harvard and Prof. David
of Lyon, have allowed specimens in their charge to be examined. Prof. J. E. Smith
made available the facilities of the Marine Biological Station, Plymouth and Dr.
D. B. Carlisle introduced me there to living tunicates. Innumerable colleagues
have discussed the subject with the author, helping to clarify ideas, and making
many suggestions. In this respect I would particularly like to mention Dr. E. I.
White, M. J. Chauvel, Dr. R. Prokop, Dr. Q. Bone, Dr. G. Underwood, Dr. D. B.
Macurda, Prof. J. Wyatt Durham, Dr. N. J. Holmes, Dr. M. H. Hey, Dr. C. Patterson
and Dr. C. R. C. Paul. Prof. Ubaghs gave the author the chance to see much
unpublished work. Our agreement on facts was combined with almost complete
disagreement on interpretation. Mr. P. Minton generously gave several afternoons
to discussion and made numerous helpful suggestions on functional morphology
from an engineer's standpoint. Text-figures la, b ; 2 ; 4b, d; 6 ; 8a, b; n a; I3a, b,
I4a, b ; iyb ; iga ; 20 ; 21 ; 23a, b ; and 27a are reproduced here by kind permission
of the Zoological Society of London.
III. MORPHOLOGY
a. Cothurnocystis elizae Bather 1913
SYSTEMATIC POSITION: Phylum Chordata: Subphylum Calcichordata : Class
Stylophora (Gill & Caster 1960). Order Cornuta (Jaekel 1900). Family: Cothur-
nocystidae Bather 1913. Genus: Cothurnocystis (Bather 1913). Type species.
OCCURRENCE: Only known from the hard, greenish siltstone of the Starfish Bed
[Upper Ordovician, Ashgill Series, Drummuck Group]. All the material examined
was from Thraive Glen, Girvan, Ayrshire, Scotland — the type locality. The asso-
ciated fauna indicates a shallow water, marine environment.
MATERIAL: About 190 specimens collected by the Gray family and preserved in
the British Museum (Natural History). The specimens are mostly still articulated
as if suddenly buried. The plates have not been distorted by compaction of the
248 PRIMITIVE FOSSIL CHORDATES
rock. The registration numbers are as follows : £23130-1, £23133-7, £23139-41,
£23143-50, £23152-9, £23161-4, £23166-7, £23169-72, £23174-86, £23188-93,
£23201, £23318, £23329, £23337, £23342, £23352, £23394-6, £23702-5, £23713,
E 23716-7, E 23719-27, E 23729, E 23731-7, E 23740-3, E 23745, E 23747, E 23749,
£23752-3, £23757, £23761, £23766, £28417, £28420, £28571-3, £28575,
£28590-1, £28603-8, £28631-2, £28635-46, £28651, £28654, £28656-60,
£28663-4, £28666-7, £28884.
GENERAL SHAPE AND PLATE NOMENCLATURE: (Fig. la-g).
The animal consists of a theca and a stem. The theca is boot-shaped and, follow-
ing Bather, an " ankle " and a " foot " part can be distinguished. The thecal
skeleton consists of stout marginal plates to which are attached upper dorsal and
lower ventral flexible integuments (" obverse " and " reverse " Bather 1913). The
recognition of upper and lower surfaces of the theca is virtually certain, for all the
thecal openings are on the dorsal side, and all the spikes for anchoring the theca
to the bottom are ventral. Three prominent spines project from the anterior
face of the theca and can be called the right oral appendage, left oral appendage and
left appendage (tag, tongue and toespine of Bather 1913: 399; digital, glossal
and spinal of Ubaghs 1963).
The marginal plates are numbered to right and left starting anterior to the stem
and finishing at the mouth, the complete assemblage being as follows:
Ubaghs 1963.
Based on plate
notation of
Notation Name Bather 1913 Jaekel 1900
MILD first left dorsal marginal Not shown Not shown
MILV first left ventral marginal 5 Mx
M2L second left marginal 6 M2
Mat, third left marginal 7 M3
M4L fourth left marginal (incl. left appendage) 8 (incl. toe spine) M4 (incl. spinal)
MSL fifth left marginal 9 and 10 Mg and M6
loap left oral appendage tongue glossal
sixth left marginal n M7
first right dorsal marginal Not shown Not shown
first right ventral marginal 4 Mt'
M2R second right marginal 3 M2'
MSR third right marginal 2 M3'
M4R fourth right marginal i M4'
roap right oral appendage tag digital
MSR fifth right marginal 12 M5'
A strut on the ventral surface connects MIR and MSL- Distinct spikes (S) are
present on the ventral surfaces of M.zn (Sn), M2L (SIL), and MSL (Sai,)- Sutures
are indicated MILD/V, M2/3R etc.
The stem consists of three distinct parts: anterior, medial and posterior. The
nomenclature used will be discussed later (p. 25911).
THECAL OPENINGS: The openings of the theca are anatomically crucial and have
caused much argument.
WITH ECHINODERM AFFINITIES
249
roap
M
FIG. i. Cothurnocystis elizae. Reconstruction of external features, a. dorsal ; b. ventral
aspect ; c. stem from left ; d. theca from left ; e. " ankle " region from left ; f. theca
from right ; g. posterior aspect, an = anus ; dp = dorsal plate of posterior stem ;
lap = left appendage ; loap = left oral appendage ; roap = right oral appendage ;
stc = stylocone ; str = strut ; vo = ventral ossicle without boss ; vob = ventral
ossicle with boss.
250
PRIMITIVE FOSSIL CHORDATES
r\
2L
WITH ECHINODERM AFFINITIES
FIG. ic.
251
lap
FIG. if.
roap
M
M.LD MIRD
an /
M2R
t
252
PRIMITIVE FOSSIL CHORDATES
WITH ECHINODERM AFFINITIES 253
There were, first, about 16 elliptical openings (bs) in the left, posterior part of
the dorsal integument. Their detailed structure (Fig. 2 a-c; PL i, figs, i, 7, 8) can
best be studied with latex casts. Each opening is surrounded by a frame consisting
of a smaller anterior u-shaped plate (au) and a larger posterior one (pu) with an
articulation between them. The anterior dorsal part of the anterior u-plate bears
an antero-dorsal process (adp), of very variable size. Posterior to this process a
flap (f) is attached by flap attachment facets (faf). This flap is convex outwards
and concave inwards and contains many small plates which are often bigger towards
the margins than in the middle of the flap. The flap must have been flexible in
life and the edges of its free, posterior part were able to rest on the posterior u-plate,
so as to shut the opening completely. There is no doubt that the flap was attached
to the anterior u-plate rather than the posterior one since, when these two plates
were displaced relative to each other after death, the flap was sometimes displaced
to one side of the posterior u-plate (flaps f in PL i, fig. 8) but remained connected
to the anterior u-plate in the normal way. The posterior, internal end of the
posterior u-plate was produced into a flat-topped reniform process (rp in Fig. 2a ;
PL i, fig. i).
Bather's descriptions of these openings (1913 : 404, fig. 16) is very different from
the above except as regards the two u-plates of the frame. In his view the small
plates inside each slit were biserial " cover plates " attached to the edges of the
posterior u-plate. This interpretation may have been suggested by the fact that
the plates round the edge of each flap tend to be larger than those in the middle.
Using latex casts, however, which were not of course available to Bather, the attach-
ment of the flap to the anterior rather than the posterior u-plate can easily be
demonstrated.
The structure of these openings strongly suggests outlet valves. When the water
pressure beneath the branchial slits increased, the flaps would lift from the posterior
u-plates. This would happen partly because of the flexibility of the flaps, and
partly because the frames of the slits would bend upwards at the articulations
between anterior and posterior u-plates, to follow the bulging of the integument.
When the flaps opened water would escape. As the water pressure beneath the
openings consequently decreased, the flaps would close and prevent water from
entering. The outwardly convex, arcuate section of each flap, maintained by the
u-shape of the anterior u-plate and by a slight stiffness imparted by the little plates
of the flap, is admirably suited to resist pressure from outside and confirms the
outlet valve interpretation. This interpretation is also supported by the presence
of a differently constructed outlet-valve system in a corresponding position in
C. curvata (p. 266). The slits of both species do not resemble inlet structures and
Bather's view that they were mouths, resting as it does on the interpretation of the
flap plates as biserial cover plates, is without foundation. It is unlikely that the
slits were gonadial (pace Jaekel 1918 : 122) or excretory since a much less elaborate
structure would, in these cases, suffice. By far the most probable interpretation
is that they were exhalent and homologous with branchial slits, as Gislen suggested
(1930 : 213).
Another opening, not mentioned in the literature (an in Figs. la, g, Fig. 3a, d ;
254
PRIMITIVE FOSSIL CHORDATES
CD
a o .a
C HH r-H
WITH ECHINODERM AFFINITIES 255
PI. i, figs. 2, 10) whose function was clearly different from that of the gill slits, lies
just posterior to the most median of these, to the left of the stem, on the suture
MILV /MILD- It connects with a groove (rg) which first goes down vertically between
MILV and MILD and then turns to the right and runs over the dorsal surface of the
horizontal flange of MILV and MIRV (hf in Fig. 3c; PL 2, fig. 8). This groove could
well represent the course of the rectum, in which case the opening connected to it
would be the anus. Such an interpretation is confirmed by the position of the open-
ing, for the streams of water from the most median gill slits, flowing backwards
parallel to the flaps, would serve to wash faeces away from the anus. The opening
is, incidentally, far too large to have been a hydropore.
The only other thecal opening (mo in Fig. la; PI. 2, fig. 4) lies at the anterior
end, between the right and left oral appendages. The pointed plates round this
opening give it the appearance of an anal pyramid, as Bather asserted (1913 : 412).
However, there is no compelling reason why such a structure must have served
as an outlet, and indeed, if the other openings represent gill slits and anus, then
this last opening can only be the mouth, as Gislen suggested (1930 : 213). This
agrees with the fact that it is much the largest opening in the theca.
An interesting peculiarity of preservation supports the present interpretation
of the thecal openings. As already stated the specimens studied seem to have
died by sudden burial. It is sometimes found (specimens E 23148, E 23150, E 28641)
that the integuments of the theca to the right, but not to the left, of the strut are
separated by a layer of rock. This is presumably because the fall of mud that
killed the animal, entered the mouth before this had time to close and filled up the
right-hand side of the theca. On the other hand, only a very small amount of mud
could enter through the gill slits, whose flaps would shut when mud was piled on
top of them.
THE CHAMBERS OF THE THECA : The features of the internal cast, integuments
and external shape of C. elizae indicate that the theca was divided into four chambers
(Fig- 4)-
The existence of the first of these chambers, filling the " ankle " part of the
theca, is shown by : — (a) The constant presence of a low ridge running dorso-ventrally
on the inside of MSR, just opposite the sharp angle in MSL which separates " ankle "
from " foot " (rbcr in PL i, fig. 7; PL 2, figs, i, 3; PL 3, fig. i). (b) The presence
in two specimens (rbcl in PL 3, fig. i, and E 23725) of a corresponding, parallel
ridge on the inside of M5L. In these specimens this ridge is obviously distinct
from the sharp angle just referred to, though in other specimens it is presumably
inseparable, (c) The plating of the dorsal integument of the " ankle " is different
from that of the " foot " (see below, p. 258). (d) The gross separation between
ankle and foot visible externally. This first chamber, here called the buccal cavity,
is probably homologous with the buccal cavity of chordates and the vestibule of
crinoids.
Considering now the " foot " part of the theca, an undulating line can often be
seen on the internal mould separating an upper from a lower part (pvl in Fig. 3b,
e; PL i, fig. 9; PL 2, figs. 2, 5). Followed from left to right (Fig. 4) the line rises
from the ventral margin at point o/i on MSL, reaches a peak at point i, on the
256
PRIMITIVE FOSSIL CHORDATES
suture M2/3L, descends to near the ventral border again at point 1/2 in the middle
of M2L, and rises to the dorsal margin of the frame at point 2, on MILD, just to the
right both of the anus and of the most median gill slit. It leaves the dorsal margin
at point 3, on MIRV and descends vertically to point 3/4, which is just above the
ventral border of the marginal frame. It then rises to point 4, near the suture
, falls to point 4/5, situated at the " heel " in the middle of M2R, and
FIG. 4. Cothurnocystis elizae. Chambers of the theca. a. left ; b. dorsal ; c. right ;
d. posterior aspects, o/i, 1/2, 3/4, 4/5 = points where pharyngo-visceral line nears or
reaches the ventral side of theca. i, 2, 3, 4, 5 = points where pharyngo-visceral line
nears or reaches dorsal side of theca. Stipple used as in Text-fig. 14.
WITH ECHINODERM AFFINITIES 257
then rises to point 5 on MSR, some distance behind the posterior border of the
buccal cavity. In very large specimens (PI. 2, figs. 2, 5; Fig. 3) the area of the
the internal mould above this undulating line is horizontally striated (sp). There
is no trace of the lower chamber on the inside of the frame along the anterior margin
of the " foot " part of the theca.
This undulating line gives the strong impression of separating two chambers and
the striae above it confirm that the area dorsal to it corresponded to one and the
same chamber. This upper chamber must have opened by the gill slits as is con-
firmed by the fact that, on the front surface of MILD, its distribution coincides
with the presence of slits in the dorsal integument. The upper chamber must
therefore have been the pharynx and, if so, the lower chamber would be the main
visceral cavity, henceforward called the anterior coelom. The main mass of the
viscera would have lain on the ventral integument somewhat to the right of, and
anterior to, the stem. It is from this general region that the rectal groove emerges.
The separate existence of buccal cavity and pharynx is supported by hydrodynamic
considerations and by peculiarities in the plating of the integuments (see below,
p. 258). The undulating line will henceforward be termed the pharyngo-visceral
line.
The peaks in the pharyngo-visceral line at points I and 4, which are near the
sutures M2/3L and Mmv/2R, may be due to the optic nerves ascending almost to
the dorsal side at these points, for the optic nerves of Mitrocystites mitra break
through on to the dorsal surface at corresponding positions. This implies that at
their first appearance in the cornutes the optic nerves were totally internal and came
into existence before the eyes, in accordance with Studnicka's theory (Walls 1942 :
126). Totally internal optic nerves would have been quite capable of functioning
as light sensors. The gradual ascent of the pharyngo-visceral line between points
4/5 and 5 reflects the fact that pharynx and buccal cavity had to be connected,
for obvious reasons, so that the anterior coelom in this region was pushed over to
the right.
The last chamber (posterior coelom in Fig. 4; pco in PI. i, fig. 9; PI. 2, fig. i) lay
just anterior to the stem and was largely bounded by skeleton. Anteriorly it
seems to have had a roughly hemispherical limiting membrane (mpc in Fig. 3c) which
touched the skeleton (i) at the posterior surface of MILD and MIRD, and (ii) on the
dorsal surface of the horizontal flanges (hf) of MILV and MIRV, in the shallow, curved
depression limited anteriorly by the ridge rpc (Fig. 36, C.). The rectum (r in
Fig. 3C), whose course is indicated by the rectal groove (rg), ran beneath this chamber,
from right to left, and was presumably coated dorsally by the limiting membrane
of the chamber. The posterior limit of the chamber would correspond more dorsally
to the front of the brain. More ventrally it would correspond to the front of the
vertical flanges (vf) of MILV and MIRV- The posterior coelom is probably homo-
logous to the aboral coelom of echinoderms.
To sum up, therefore, the four chambers recognizable in the theca of C. elizae
were the buccal cavity, pharynx, anterior coelom and posterior coelom. The same
chambers can be demonstrated, with variations and additions, in the other forms
studied.
GEOL. 16, 6. 26
258 PRIMITIVE FOSSIL CHORDATES
THE INTEGUMENTS AND MODE OF FEEDING: In very young specimens all the
plates of the integuments were almost uniformly polygonal with rounded corners.
In middle-sized individuals, however, there was considerable differentiation (Fig.
la, b; PI. i, fig. 7; PI. 2, fig. 3). As regards the dorsal integument, in the "ankle"
region it contained polygonal plates while in most of the " foot " it contained large,
circular or spheroidal plates. In the gill slit region it contained very small, rounded
plates and must have been very thin. The ventral integument in middle-sized
individuals contained (Fig. ib ; PI. 2, fig. 3) polygonal plates except in a crescentic
region near the anterior side of the " foot " (acp in PL 2, fig. 3), mainly left of the
strut, where the plates were circular. In all cases circular plates touched their
neighbours, if at all, at only five or six points, whereas polygonal plates touched
their neighbours all round their edges. The integuments of large individuals
(PL i, fig. 10 ; PL 2, fig. i) were like those of middle-sized ones except that the plates
of the whole of the dorsal integument, save the small plates of the gill slit region,
were large and circular. In the " foot " region, however, the plates of this integu-
ment were separated by larger spaces than those of the ankle region, which is
comparable to the condition in middle-sized specimens.
The functional significance of the different sorts of integumental plates is related
to the underlying thecal chambers. Wherever the pharynx touched the integuments,
except in the gill-slit region, the plates tend to have larger interspaces than elsewhere.
This applies both to the dorsal integument over most of the " foot " region and to
the left, anterior part of the ventral integument. Such interspaces could well have
contained muscles, and the corresponding parts of the integument would have
been involved in pumping. The thin, small-plated integument of the gill-slit
region would have been very flexible, which would clearly have made the region
more efficient as a valve. The integument of the buccal cavity and the parts of
the ventral integument on which the anterior coelom rested would not have been
so directly involved in pumping as the parts touching the pharynx, and were
consequently less well muscled.
If the pharynx was the main pumping region it would be hydrodynamically
advantageous to have a valve just upstream of it, at its anterior end, to prevent
forward flow. This valve, between pharynx and buccal cavity, would be the
velar valve. Water may have entered the pharynx from the buccal cavity by
muscular outward flexing of the pharyngeal regions of the integuments or through
being driven in by cilia lining the buccal cavity and pharynx. Expulsion of water
from the pharynx must have been by contraction of the muscles of the pharyngeal
walls. Such contraction would tend to pull the frame inwards and to cause collapse
at the middle of the anterior part of the frame, which is convex inwards. The strut
in the plane of the ventral integument is perfectly placed to prevent such collapse.
Phylogenetically speaking, this strut is a remnant of the completely rigid ventral
shield of the Upper Cambrian Cothurnocystis americana Ubaghs 1963, in which
there was a dorsal integument, and of the ventral skeleton of the Middle Cambrian
Ceratocystis perneri Jaekel, where the whole theca was rigid.
C. elizae must have been a " deposit feeder ", in Hunt's terminology (1925 : 567),
grazing on " the detritus deposited on the bottom and associated micro-organisms."
WITH ECHINODERM AFFINITIES 259
This is apparent since the mouth was about level with the sea bottom and since
the inhalent current could only have been horizontal. The right oral appendage
has sharp edges, an almost flat lower surface and a convex upper surface, and is
articulated by a vertical ridge on its base to a corresponding ridge on M4R, (PI. 2,
fig. 4). The articulation is flanked by spaces that could well have contained muscles.
This appendage seems to be adapted for waving from side to side, scraping and
churning-up the surface layer of the sea bottom. The resulting suspension would
be sucked in through the mouth. It is advantageous to a deposit feeder to move
over the surface, grazing the bottom as C. elizae was probably able to do (p. 265).
By contrast, C. curvata was probably a suspension feeder, which explains the coexist-
ence of the two types as well as many points of difference (p. 271). In both species
food particles would presumably have been carried into an oesophagus by mucus
streams on the internal surface of the pharynx.
stem ossicle
peduncular
'nerve
chambered
organ
tperihaemal space
haemal strand
FIG. 5. Transverse section of the stem of a crinoid, based on Reichensperger (1905).
A curious feature of some young specimens is a number of specially large plates
(crestal plates, cp in PI. i, fig. 2) in the dorsal integument. These correspond in
position to a clearly marked line of plates in Cothurnocystis americana (Ubaghs 1963)
and to the carinae on the dorsal surface of Ceratocystis perneri. In C. elizae their
appearance is only sporadic and they were probably non-functional.
THE STEM: The nearest living analogue to the stem of a stylophoran is the stem
of a crinoid. The probably ancestors of crinoids were the eocrinoids which include
forms with distinct stems from the Middle Cambrian (Gogia Walcott, see Robison
1965). These are roughly contemporary with the first cornute so that, in view
of the obvious gaps in the record, there is no chronological reason why the stems
of crinoids and Stylophora should not be homologous.
The stem of a crinoid will now be compared with the tail of a fish. The best
anatomical account of a stalked crinoid is that of Reichensperger (1905) (see Fig. 5).
The central lumen of the stem contains, on the outside, the peduncular nerve, with
the fibres running longitudinally. Inside this is the chambered organ, a turgid
structure consisting of five adjacent tubes. Inside this is a space (here called the
260 PRIMITIVE FOSSIL CHORDATES
perihaemal space) in which lies a narrow tube called the haemal strand. The top
of the chambered organ is at the proximal end of the stem. Here the five constituent
tubes swell slightly and bend inwards to touch the haemal strand, so separating
the perihaemal space of the stem from the thecal cavity. The haemal strand con-
tinues out of the stem into the theca, where it joins the axial organ. The haemal
strand presumably functions as a blood vessel, since otherwise it is difficult to see
how nutrients could reach the stem. Round the top of the chambered organ is
situated the aboral nerve centre, which is the meeting-place of the aboral nerves
of the theca with the peduncular nerve. The chambered organ presumably func-
tions as the hydrostatic skeleton of the stem, helping to hold the ossicles in alignment.
It is of mesodermal origin, arising as five pouches of the aboral coelom (Seeliger
1892). The origin of the aboral nervous system has never been seen, but it appears
to arise later than the chambered organ.
Though never reported, muscles must exist in a crinoid stem which, in larval
Antedon, can be bent at will (Chadwick 1907 : 37; Dimelow 1959 : 21). Hyman
(1955 : 60) has pointed out that some of the " elastic " fibres in the cirri must be
muscular, since these organs also can be bent at will. Elastic fibres have been
reported in the stem itself, and if some of these are muscular then the nerves going
from the peduncular nerves to the stem ossicles, which so puzzled Reichensperger
(1905 : 30), could be their nerve supply.
The resemblances of a crinoid stem to a fish's tail are very striking. The chambered
organ is like the notochord in structure, presumably in function, and to a lesser
extent in origin. The peduncular nerve can be compared with the dorsal nerve
cord, being applied to the surface of the chambered organ as the dorsal nerve cord
is applied to the notochord. The aboral nerve centre is like the brain, for it lies
at the "anterior" end of the chambered organ (= notochord) and peduncular
nerve (= dorsal nerve cord) and sends out aboral (= cranial) nerves into the theca.
The muscles which must exist in the stem would correspond broadly to those of
the tail. The haemal strand and perihaemal space could correspond broadly to
caudal artery and veins.
Furthermore the aboral nerve centre is physiologically the brain of a crinoid.
Thus Langeloh (1937 : 272) showed that if it is excised the animal becomes limp
and fails to carry out complicated patterns of behaviour which are otherwise in-
stantaneous. If, however, an electric current is applied to the site of the excised
centre, the appropriate reaction follows at once. The centre functions not so much
in co-ordination as in summation of stimuli. In this it resembles the brain of a
fish (Gray 1936; Gray & Sand 19360;, b).
A crinoid stem certainly differs from a fish's tail in a number of ways. It is
pentameral, with the homologue of the notochord divided into five parts and com-
pletely surrounded by the homologue of the dorsal nerve cord. Also the stem has
a calcite skeleton, has the haemal strand inside the chambered organ and is attached
distally. The stylophoran stem was intermediate, for it certainly had a calcite
skeleton, probably had a " haemal strand " or peduncular vessel inside the noto-
chord, and may have been attached distally when very young. On the other hand
it lacked all sign of pentamery, in common with the theca, and, at least in mitrates,
WITH ECHINODERM AFFINITIES
261
had the dorsal nerve cord exclusively dorsal to the notochord. Also the segmenta-
tion of a fish's tail almost certainly corresponds with that of a stylophoran stem
as regards the soft parts, but probably not with that of a crinoid stem. The corres-
pondence of a crinoid or stylophoran stem with a fish's tail agrees with Marcus's
statement (1958 : 50) that " the metamerism of the chordate trunk is fundamentally
a subdivision or multiplication of the metacoel ".
Iqa
mq
FIG. 6. C. elizae. Block diagram of portion of posterior stem, dnc = dorsal nerve
cord; dp = dorsal plate ; fdp = facet for dorsal plate ; Ibv = lateral blood vessel ;
Ig — lateral groove ; Iga = lateral ganglion ; In = lateral nerve ; Ipt = lateral pit ;
mg = median groove ; mu = muscle ; not = notochord ; nv = notochordal vessel ;
vo = ventral ossicle ; tg = transverse groove.
The stem of C. elizae will now be described, beginning at the posterior end where
the skeleton is most complicated and informative.
The posterior stem (Fig. i, 6; PI. I, figs. 4, 5, 7 ; PL 2, fig. 9 ; PI. 3, figs. 2, 3) consists
of about 60 segments and ends abruptly. Each stem has a solid, hemicylindrical
ventral ossicle (vo) and a dorsal arch formed of paired dorsal plates (dp) which meet
mid-dorsally at a suture. Each dorsal arch imbricates over the front of the one
behind it. Near the middle part of the posterior stem some of the ossicles project
ventrally in a boss (Fig. ic; PI. i, fig. 4) and the posterior faces of such ossicles
262 PRIMITIVE FOSSIL CHORDATES
are not plane, but curved about a horizontal axis. Such cylindrical surfaces would
make it easier to bend the column of ventral plates vertically (Fig. 7) and it follows
that the middle part of the posterior stem was vertically more flexible than the
more anterior part. Towards the posterior end of the stem, the ventral bosses
coalesce to form a blunt ventral keel.
The dorsal surface of each ventral ossicle is complicated (Fig. 6; PI. 2, fig. 9).
There is a median groove (mg) which runs the length of the posterior stem and
connects anteriorly with the lumen of the stylocone. On each side of this groove
FIG. 7. A. Plane, and B. cylindrical interossicular joints. Bending at a plane joint
involves compression or dilatation, or both, of the interossicular soft tissue. Bending
at a cylindrical joint can occur by torsion of the soft tissue.
are lateral grooves (Ig) which on each ossicle are deepened into lateral pits (Ipt).
Outside the lateral grooves are facets for the reception of the dorsal plates (fdp).
Paired transverse grooves (tg) connect the lateral pits with the median groove.
The median groove of C. elizae probably contained the chambered organ or
notochord, coated, at least partially, with the peduncular nerve or dorsal nerve
cord. By analogy with the mitrates the nerve was perhaps restricted to the dorsal
surface as shown in Fig. 6. The imbricate dorsal plates show that the posterior
stem could flex upwards. For this, muscles (mu) would be needed. They would
lie in the space between dorsal plates and ventral ossicles and would be seated in
the lateral grooves. They were probably divided into muscle blocks, the divisions
between which, by analogy with C. curvata and the mitrates, would correspond to
the transverse grooves. Muscles would need nerve and blood supply. The trans-
verse grooves may possibly mark the course of lateral blood vessels connected with
WITH ECHINODERM AFFINITIES 263
a central peduncular blood vessel (nv in Fig. 6) in the notochord that was homologous
with the haemal strand of crinoids. Along the dorsal surface of the lateral blood
vessels, by analogy with the mitrates, lateral nerves may have run. The extensor
force opposing the muscles was probably due to the column of ventral plates which
may have been elastic like a recent crinoid stem when wet (personal observation).
The abrupt end of the posterior stem is of some interest. It strongly suggests that
at some stage in the life history the stem extended posterior to what now remains.
Indeed, it is possible that when very young the animal was attached by a holdfast,
like a crinoid, from which it later broke free. An abrupt end to the stem is also
found in all the other forms studied.
Ubaghs (ig6ib) has interpreted the structures of the posterior stem of both
cornutes and mitrates as representing a water vascular system (median groove =
main water vessel; lateral grooves = lateral water vessel; lateral pits = sites of
tube feet; dorsal plates — cover plates; stem as a whole = arm of asterozoan).
This seems quite unacceptable for reasons which will be set out in detail after the
mitrates have been discussed.
The medial stem (Fig. i ; PI. i, figs. 3, 4, 7) corresponds to two segments and is
made up of the stylocone (stc) ventrally and two pairs of plates dorsally. The
large anterior cavity of the stylocone connects with the median groove of the posterior
stem and is flanked by two pairs of lateral pits, with transverse grooves leading
to them. The stylocone resembles two fused ventral posterior stem ossicles, with
which it is serially homologous. It is also presumably homologous with the paired
ventral plates of the anterior stem. It served as a rigid barrier to separate the
powerful muscles of the anterior stem, which moved the stem sideways, from the
muscles and ventral ossicular column of the posterior stem, which moved it up and
down. If the muscle blocks of the posterior stem and anterior stem had formed
continuous columns, separated only by myocommata, then contractions of the
anterior muscles would have produced functionally irrelevant elongations of the
more anterior muscle blocks of the posterior stem on one side only.
The anterior stem is offset downwards from the theca (Fig. ib, c), so that its
median ventral line is lower than the ventral surface of the latter. It consists of
five rings of plates (cf. Ubaghs i()6ia; Caster 1952) enclosing a large lumen. Each
ring has four plates — left, dorsal and ventral and right, dorsal and ventral — denoted
by DHL, VSnL and DOR and VSnn in ring n. The dorsal plates are much smaller
than the ventral plates. Each one is apposed to its antimere at the median line
and imbricates below the corresponding ventral plate ventrally. The dorsal plates
are evidently serial homologues of those of the medial and posterior stem.
The ventral plates of the anterior stem are crescentic in anterior or posterior
aspect. They are therefore thinner near their dorsal and ventral ends than near
the middle. The posterior surface is always almost plane. The anterior surface
is either almost plane or produced into an admedian imbrication flap (if in PI. i,
fig. 10) which is not developed near dorsal and ventral ends of the plate.
The length of a ventral plate, measured along the length of the stem and omitting
the imbrication flap, is greater near the mid-line than more laterally (PL i, fig. 10).
Successive pairs of ventral plates touched each other ventrally, without imbrication,
264 PRIMITIVE FOSSIL CHORDATES
and almost touched dorsally. There would therefore, when the anterior stem was
held straight, have been gaps between successive plates at right and left, and these
would have allowed lateral flexing.
The first pair of ventral plates (VSiL, VSm) fitted into a reception groove in
MIRV and MILV (reg in Fig. 3d). The gap between the corresponding dorsal plates
(DiL, DIR,) and the arch formed by MILD and MILD and MIRD was filled by a pair
of dorsal plates (DQL and DOR) with no ventral plates corresponding.
The skeleton thus shows that the anterior stem was adapted to flex sideways
but not up and down, and the way the specimens are preserved confirms this. The
anterior stem is found flexed in any position from extreme right to extreme left
as it lay at the moment of burial (e.g. PI. i, figs. 4-7). The soft parts of the anterior
stem must have consisted mainly of powerful muscles, presumably divided into
segmental blocks. An anti-compressional structure (notochord or chambered
organ), which would have maintained the alignment of the skeletal rings, is likely
to have existed. It would be a forward continuation of the notochord of the
posterior and medial stem, would contain the peduncular blood vessel and would
be coated by the peduncular nerve or dorsal nerve cord. Segmental nerves and
blood vessels to the muscles must also have been present.
THE BRAIN : By analogy with a crinoid the aboral nerve centre or brain of Cothur-
nocystis elizae must have occupied a prominent basin (cerebral basin, ceb in Fig. 3)
excavated in the postero-ventral faces of MIRV and MILV where the stem joins
the theca (PL 2, fig. 6).
A median notch (nmln) in the dorsal edge of plates MIRV and MILV leads to
two grooves (gmln), running outwards and downwards, on the anterior face of the
vertical flange (vf) of these plates (Fig. 3, PI. 2, fig. 8). The left groove can some-
times be followed to the floor of the rectal groove (PI. 2, fig. 7). The right groove
is somewhat shorter, probably because the structure that it carried left the skeleton
earlier. To right and left of the median notch are two triangular depressions (pbd)
excavated in the dorsal surface of MIRV and MILV-
The soft structures indicated by the notch, grooves and depressions, since they
came off the brain, were probably nervous. The depressions probably carried
ganglia, corresponding to the pyriform bodies (pb in Figs, iga, 27a) of mitrates.
The grooves probably carried nerves (median line nerves) . Since the left one passed
under the rectum this, at least, was more ventral than any nerves of which there
is evidence in mitrates, with the possible exception of the nerves n0. The optic
nerves, whose possible terminations have been indicated above, presumably left
the brain more dorsally, through the notch, and passed dorsal to the rectum.
ONTOGENY: Very small specimens much resemble adults. At a length (measured
from the stem base to the anterior end of MSL) of 6 mm., gill slits already existed
and extended back to the anus, as in the adult. Their number could not be
determined. The smallest specimens (e.g. PI. 2, fig. 4) do not have the stem offset
ventrally with respect to the theca and lack ventral spikes, which first appear on
the sides of the marginals. The number of rings in the anterior stem is smaller
(only 3 in PL i, fig. 3) and the number of ossicles in the posterior stem is about
WITH ECHINODERM AFFINITIES 265
fifteen, as opposed to about 60 in the adult. The smallest specimens have the
ventral mouth frame oblique to the " ankle " region, the left end being more
anterior than the right.
POSTURE AND MOVEMENT: The bizarre shape of C. elizae calls for a reconstruction
of its habits (cf. Bather 1913 : 415; 1928; Gislen 1930 : 217).
As Bather and Gislen said, the theca must have rested on the sea bottom, supported
on the ventral processes and anterior appendages, and with the dorsal surface
upwards. The right oral appendage was motile (see above, p. 259). Ot the remain-
ing fixed processes and appendages, four are roughly parallel to each other (the
left-hand spikes SIL and 821,, and the left oral and left appendages), whilst the
remaining one (the right-hand spike SR) is perpendicular to the others, cf. Fig. ib.
In life the anterior appendages would have dipped down anteriorly into the mud.
The spikes SIL and SZL, (PI. I, fig. 6) have sharper points anteriorly than posteriorly.
SR is always flat-bottomed and SIL sometimes so.
When at rest on the bottom the theca could not have moved anteriorly, for the
appendages and left-hand processes would have been forced into the sea-floor.
This is the more true since SR,, which ends ventrally in a flat suitable for resting on
the sea-floor, and the anterior stem, which is distinctly offset ventrally, would have
raised the posterior part of the theca. The theca appears to be adapted to slip
posteriorly in a direction parallel to the two fixed appendages (lap and loap) and
the two left-hand spikes (SiL and S2L), and perpendicular to the right-hand spike
(SR). The obvious motility of the stem supports Gislen's suggestion (1930 : 217)
that it was the main organ of movement. It is suggested here that it acted by pulling
the theca backwards across the sea floor in the direction indicated above. The
sea floor would be gripped by the ventral bosses on the posterior stem and by bending
the tip downwards. The power stroke would be applied by flexing the anterior
stem to left or right as appropriate.
Such a mode of operation explains: i. the specialization of the parts of the stem
for different planes of flexion; 2. the exact forms of the spikes and fixed appendages
of the theca, which would serve admirably to prevent yawing and also to prevent
forward movement during the return stroke of the stem; 3. the concentration of
ventral bosses for gripping the sea-floor, and curved interossicular surfaces for
downward flexion in the middle and posterior parts of the posterior stem.
Many features show that, when resting on the sea-floor, the usual direction of
movement of the other forms studied was also backwards.
b. Cothurnocystis curvata Bather 1913
SYSTEMATIC POSITION: See C. elizae. Both species belong to the Family Cothur-
nocystidae. Professors Caster and Ubaghs are about to create a new genus for
C. curvata (personal communication). This is certainly justified.
OCCURRENCE: As C. elizae.
MATERIAL: About 40 specimens, collected by the Gray family and preserved in
the British Museum (Natural History). The registration numbers are as follows:
£23128, £23132, £23142, £23151, £23160, £23165, £23168, £23173, £23701,
266 PRIMITIVE FOSSIL CHORDATES
£23715, E23728, £23738, £23739, £23744, £23748, E23750-I, £23754, £23756,
£23758, £23767, £28427, £28551, £28552, £28555, £28574, £28609, E286I7,
£28630, £28633-4, £28647-50, £28652-3, £28655, £28661-2, £28665. Also
G.S.M. 60839 from the Geological Survey & Museum, London and 1958.1.252 from
the Royal Scottish Museum, Edinburgh.
GENERAL SHAPE AND PLATE NOMENCLATURE: The general shape of the theca
(Fig. 8a-e) is much like C. elizae but more symmetrical. The most obvious difference
is the presence of only one oral appendage — a fixed structure probably corresponding
to the left oral appendage of C. elizae. In addition the anterior part of the theca
is convex upwards, whence the specific name. The marginal plates are numbered
according to the scheme used in C. elizae, but homologous plates do not always
bear the same numbers, as the table below shows.
C. curvata
Bather 1913 Present notation Homologous plate in C. elizae
Not shown MILD MILD
5 MILV MILV
6 and 7 M2L M2L
M3L
8 MSL left appendage M,JL left appendage
M4L
9, 10 and n MSL anterior strut plate MSL anterior strut plate
Not shown right appendage left oral appendage
M6L
Not shown MIRD MIBD
4 MIRV MIRV
3 M2R
M3R M2R
2 M4R bucco-pharyngeal plate MSR (bucco-pharyngeal plate
bearing bucco-pharyngeal
ridge)
i M5B M4R
M5R
and the right oral appendage of C. elizae are not represented in C. curvata.
M2R, M4L of C. curvata are not represented in elizae.
Ventral spikes were present on M2R, MSR and sometimes M4R (see PI. 3, fig. 7), and on
M2L- These spikes are denoted respectively as SIR, S2R, SSR and SL.
THECAL OPENINGS: The branchial slits (Fig. 9; PI. 3, figs. 2, 3, 4, 7) are situated
much as in C. elizae but number about 40 and differ in structure. The slits are
separated by chevron-shaped plates (interbranchial chevrons, ibc in Fig. 9) each
of which fits accurately against its neighbours. The low crest of the chevron (cr)
points outwards and may represent a suture, for it often fractures. Each inter-
branchial chevron has grooves in its sides just above the ventral margin (arcuate
grooves, arg in Fig. 9) . These grooves end anteriorly and posteriorly as the cavities
WITH ECHINODERM AFFINITIES
267
of hollow processes (anterior and posterior excavate processes, aep, pep in Fig. 9).
Most of the ventral surface of the chevron is occupied by a ventral groove (vg)
which is widest beneath the crest of the chevron. The rest of the ventral surface
is occupied by the ventral walls of the arcuate grooves except for anterior and
posterior semicircular tabulate areas at the tips of the chevron.
3R
M
2L
FIG. 8. Cothurnocystis curvata. Reconstruction of external features, a. dorsal; b. ventral
c. anterior ; d. posterior ; e. left ; f. right aspects, bs = branchial slit ; lap = left
appendage ; rap = right appendage ; stc = stylocone ; str = strut.
268
PRIMITIVE FOSSIL CHORDATES
The branchial complex almost certainly acted as an outlet valve. It was mounted
in a flexible integument. When the pressure was high beneath this integument
the complex would belly out, the chevrons would separate from each other and
water would escape. When the internal pressure consequently decreased the
integument would deflate, the chevrons would clap together and water would be
unable to enter. The crests of the chevrons would coincide with the line of greatest
'2R
FIG. 8b.
WITH ECHINODERM AFFINITIES
269
FIG. 8c.
M
FIG. 8d.
M
ILD
StC
FIG. 8f.
270
PRIMITIVE FOSSIL CHORDATES
stretching of the integuments, and this would increase the efficiency of the valve
mechanism.
Each arcuate groove was probably filled with connective tissue, which may have
projected slightly out of the groove when the chevrons were separate. It would
consequently press against the contents of the neighbouring arcuate groove when the
FIG. 9. C. curvata. Branchial skeleton. A. External aspect ; B. longitudinal section
through b-b ; C. transverse sections through a-a ; D. internal aspect ; E. left lateral
aspect ; F. Section through plates of integument c-c. aep = anterior excavate process;
arg = arcuate groove ; ba = base ; cr = crest ; ibc = interbranchial chevron ;
Ifc = lateral facet ; pep = posterior excavate process ; sh = shaft ; tp = top ; vg =
ventral groove.
WITH ECHINODERM AFFINITIES 271
chevrons clapped together. This would provide an excellent seal which would
increase the efficiency of the valve. The facts that: (i) the length of an arcuate
groove coincides exactly with the extent to which neighbouring chevrons touch
each other, (ii) the edges of an arcuate groove match exactly against those of its
neighbour, (iii) the ventral positions of the grooves coincide with the parts of
the chevrons that would first come together on deflation, strongly confirm this
interpretation.
By comparison with C. elizae each chevron represents the fusion of adjacent
halves of neighbouring anterior and posterior u-plates. The presumed crestal
suture of C. curvata represents the articulation between anterior and posterior
u-plates of C. elizae and also a corresponding suture through the branchial slits of
Ceratocystis perneri. The branchial valve mechanism of C. elizae depended on the
bellying-out of the integuments under pressure, the bending of the frames of the
slits, and the flexibility of the flaps. The branchial valve mechanism of C. curvata
depended only on the bellying-out of the integument.
There is no external anus in C. curvata (Fig. 8a; PL 3, figs. 9, 10). An obvious
rectal groove (rg in Fig. ua ; PI. 3, fig. 5) runs across the floor of the posterior coelom
but, instead of opening directly to the outside, joins a distal rectal canal (drc in
Fig. ua; b ; PI. 3, fig. 9) in MILD running anteriorly and dorsally. This canal leaves
MILD where only a small stretch of integument separates it from the most median
interbranchial chevrons. The anus must therefore have been internal, opening
into the most median branchial slits, downstream of any food-collecting surface
inside the pharynx.
The outlet current from the gill slits of C. curvata would be perpendicular to the
integument, instead of horizontal and backwards as in C. elizae. A very close
association of branchial slits and anus would therefore be advantageous. This
close association proves that the distal rectal canal was indeed an outlet and con-
firms the identification of the anus in C. elizae.
The mouth was surrounded by pointed plates, as in C. elizae, but was dorsal in
position. This involves no difference in the " connections " with the surrounding
skeleton, for even in C. elizae a lower lip separates the mouth from the nearest parts
of the marginal frame (M6L and MSR in C. elizae}.
The dorsal position of the mouth shows that C. curvata, unlike C. elizae, was a
suspension rather than a deposit feeder. This explains a number of other differences
from C. elizae, viz: I. the absence of the right oral appendage, which in C. elizae
was specialized in connection with deposit feeding, 2. The narrowness of the rectal
groove, which would not need to carry much mineral detritus. 3. The possible loss
of powers of movement in the adult (see p. 277), since there would be no need to
graze the sea floor.
THE CHAMBERS OF THE THECA: A buccal cavity corresponding to that of C. elizae
is indicated by: (i) the gross separation of "ankle" and "foot" region, visible
externally, (ii) the presence of a dorso-ventral ridge (rbcr) on the inside of M4R
(PI. 3, figs. 2, 7), just opposite the sharp angle (rbcl) in MSL between " foot " and
" ankle " regions, (iii) gaps between the attachment facets of dorsal and ventral
integuments visible on the internal cast both to right and left of the " ankle " region.
272
PRIMITIVE FOSSIL CHORDATES
These gaps are widest in the middle of the region and diminish and disappear both
anteriorly and posteriorly (Fig. loa, b, d; PI. 4, figs. 2, 3). They suggest a definite
chamber between the integuments in this area.
II Surfaces of integuments
fSS Edges of integuments
FIG. 10. C. curvata. Chambers of theca. a. anterior ; b. left ; c. dorsal ; d. right ;
e. posterior aspects. Skeleton assumed to be transparent and, except in ioc, the inte-
guments assumed to be opaque. Stipple of chambers as in Text-fig. 14.
WITH ECHINODERM AFFINITIES
273
The posterior coelom (pco in Fig. na; PL 3, figs. 2, 5) shows more clearly than
in C. elizae. It is floored by the dorsal faces of MILV and MIRV, roofed over by the
ventral faces of MILD and MIRD and defined antero-ventrally by antero- ventral
processes (avp) of the latter, which rest directly on MILV and MIRV- The posterior
coelom lay in front of the brain and the rectum ran in the rectal groove (rg) beneath it.
The positions of anterior coelom and pharynx cannot be deduced directly from
the superficial internal anatomy. As in C. elizae, however, the anterior coelom
probably lay mainly in the posterior, right-hand part of the theca, since the rectum
drc
M
M
IRD
FIG. ii. C. curvata. Structure of region just anterior to stem. a. dorsal aspect, with
most of MIL and RD removed ; b. anterior ; c. posterior aspect, avp = antero ventral
processes of MIL and RD ; ceb = cerebral basin ; cmln = canal for median-line nerves ;
drc = distal rectal canal ; gmln = groove for median-line nerve ; pbd = depression
for pyriform bodies ; pco = posterior coelom ; reg = reception groove for anterior
stem ; rf = rectal foramen ; rg — rectal groove.
entered the posterior coelom from this region and the space between the integuments
is much deeper to the right of the stem than to the left (Fig. 8d).
THE INTEGUMENTS : The plates of the integument (Fig. gF) consist of a polygonal
base (ba) internally, with a process arising from it. This process may have a con-
stricted shaft (sh) and an expanded top (tp), or it may be hemispherical or have
some intermediate shape. The polygonal base is everywhere in contact with its
neighbours.
Dorsal and ventral attachment facets (uiaf and liaf) for the integuments, in most
places separated by a space of varying depth, existed on the inner faces of the
marginal plates (Fig. 10; PL 4, figs. 2, 3, 5, 6, 8).
Differentiation of the integument plates is less marked than in C. elizae. The
plates of the ventral integument are smaller than those of the dorsal integument.
GEOL. l6, 6.
27
274
PRIMITIVE FOSSIL CHORDATES
Plates with hemispherical processes are commonest in the posterior right-hand
corner of the theca.
The spaces between neighbouring processes probably contained muscle. The
shortness of the processes in the posterior right-hand corner therefore suggests
that the plates here were less involved with pumping than elsewhere. This can
be related to the probable position of the anterior coelom.
FIG. nb.
req
ceb
FIG. nc.
WITH ECHINODERM AFFINITIES
275
THE STEM: The posterior stem is incomplete in all the larger specimens studied.
In E 28661, whose maximum width across the theca was 18 mm., it must have
contained more than sixteen segments. The number of segments increased in
ontogeny for in E 28552 (thecal width = 6-5 mm.) there are only nine segments in
mub
vo
FIG. 12. C. curvata. Block diagram of portion of posterior stem, admp = admedian
process of dorsal plate ; afc = anterior facet of dorsal plate ; dnc = dorsal nerve cord ;
dp = dorsal plate ; ik = internal keel of dorsal plate ; Ibr = lateral blood vessel ;
Iga = lateral ganglia ; In = lateral nerve ; mg = median groove ; mub = muscle
blocks ; tb = transverse buttress ; tg = transverse groove ; vo = ventral ossicle.
the whole posterior stem. As in C. elizae the stem, when complete, seems to have
ended abruptly.
The structure of individual segments is basically (Fig. 12 ; PI. 4, figs, i, 4) as in
C. elizae. There was a hemicylindrical ventral ossicle (vo) and a pair of dorsal
plates (dp). The dorsal surface of the ventral ossicle carried a median groove
(mg) which gave rise to a pair of transverse grooves (tg) running obliquely backwards.
Unlike C. elizae, the anterior half of the dorsal face of each ventral ossicle carried
276 PRIMITIVE FOSSIL CHORDATES
paired, hemicylindrical, transverse buttresses (tb). The dorsal plates were thicker
than in C. elizae and there is an internal keel (ik) separating an anterior internal
facet (afc) from the rest of the internal surface of the plate. The internal keel
ends ventrally in an admedian process (admp). The interface between a ventral
ossicle and a dorsal plate is of large area and complicated shape, straddling the
transverse buttress and part of the dorsal surface of the same ossicle behind the
buttress.
As regards interpretation, it is clear, firstly, that the dorsal plates, because of
their complicated ventral articulation, could not have opened outwards as Prof.
Ubaghs' hypothesis would require. Secondly, the space between dorsal plates and
ventral ossicles, which would be largely filled with muscle, is partially subdivided
by the admedian processes and internal keels of the dorsal plates. This partial
subdivision probably indicates the division between muscle blocks (mub) as shown
in Fig. 12. Thirdly, the transverse grooves, which probably carried lateral blood
vessels (Ibv) ventrally, with lateral nerves (In) and ganglia (Iga) overlying, must
have run between the muscle blocks if these were arranged as suggested. In this
they resembled the ganglia and probable lateral blood vessels of mitrates. The
posterior stem was probably stiff er in life than that of C. elizae for it is relatively
stouter, the faces between the ossicles are all exactly plane, and there was relatively
less space for muscles.
The medial stem of C. curvata differs from that of C. elizae in having three segments,
indicated by three pairs of dorsal plates, instead of two. It also has a very abrupt
posterior taper, especially dorsally.
The anterior stem is offset ventrally to the theca to an even greater degree than
in C. elizae (Fig. 8d). It has about six segments, each containing right and left,
dorsal and ventral plates as in C. elizae. All the plates of a ring imbricate every-
where beneath the corresponding plates of the ring next in front. This would give
flexibility dorso-ventrally as well as laterally. The anterior ventral plates (VSiL
and VSnt) fit dorsally in a reception groove in MILV and MIRV- More ventrally
they overlap these two plates, which again would allow vertical flexion. Between
the dorsal plates DIL and Dm and MILD and MIRD two small triangular plates
(DOL and DOR) are inserted as in C. elizae, without ventral plates corresponding.
The anterior stem would need some anticompressional structure (notochord or
chambered organ) to prevent telescoping, since compressional stresses would be
taken up by the skeleton even less than in C. elizae. A nerve cord, powerful muscles,
presumably in blocks, and a blood supply must also have existed.
THE BRAIN: The brain is much like that of C. elizae. It was contained in a
cerebral basin (ceb in Fig. nc; PI. 3, fig. 8) excavated in MILV and MIRV. The
median line nerves left the brain in a canal (cmln in Fig. nc) which bifurcates
away from the brain and leads to two grooves (gmln in PI. 3, fig. 5). There are
triangular depressions (pbd) for the pyriform bodies.
POSTURE AND MOVEMENT: There is no doubt that C. curvata lived with the dorsal
side uppermost since, as in C. elizae, all the openings are dorsal and all processes
are ventral.
The habitual direction of movement must have been backwards as in C. elizae.
WITH ECHINODERM AFFINITIES 277
This is shown by the anterior appendages, which dip downwards anteriorly, and
the spikes SIR, Szn, SSR and SL which are truncated by oblique planes, dipping
downwards anteriorly (Fig. 8e, f). The theca is more symmetrical than in C.
elizae, however, and the habitual direction of movement, parallel to the anterior
appendages, must have been more directly backwards.
The stem cannot have acted exactly as in C. elizae, for the anterior stem could
flex up and down, as well as sideways, and the posterior stem was probably relatively
stiff. The prominent anterior appendages would have prevented yawing, and
suggest that the animal, like C. elizae, pulled itself along by side-to-side movements
of the stem. The sequence was probably as follows: the posterior stem was stuck
obliquely into the sea-floor, somewhat to the left, by the action of the anterior
stem; the stem bent still more to the left, pulling the theca backwards; the posterior
stem was pulled out of the sea-floor ; the stem bent slightly to right and the sequence
was repeated on the right side.
Movement may not have been habitual in the adult, since most large specimens
have lost the oral appendage and all the posterior stem except two or three segments.
c. Mitrocystella incipiens (Barrande) miloni Chauvel
SYSTEMATIC POSITION: Phylum: Chordata. Subphylum: Calcichordata. Class:
Stylophora Gill & Caster 1960. Order: Mitrata Jaekel 1918. Family: Mitrocysti-
tidae Jaekel 1900 (as Mitrocystidae) . Genus: Mitrocystella Jaekel 1900. Species:
Mitrocystella [Anomalocystites] incipiens (Barrande 1887). Subspecies: Mitro-
cystella incipiens miloni (Chauvel 1941).
OCCURRENCE: The subspecies occurs in siliceous nodules in the " Schistes a
Calymenes " (Ordovician, Llandeilo Series) of Brittany. The main locality is le
Grand Champ de Traveusot, Ille-et-Vilaine (Chauvel 1941 : 176). Mitrocystella
incipiens incipiens occurs in the Sarka Beds (Llanvirn Series) of Bohemia, but is
usually ill-preserved. The associated fauna of trilobites, brachiopods and molluscs
indicates a shallow- water, marine environment.
MATERIAL: About 280 specimens in the Institut de Geologic, Rennes (mainly
Milon Coll.); A 46271 in the Sedgwick Museum, Cambridge (MacGregor Coll.);
two specimens in the Department of Geology, University of St. Andrews, Scotland
(MacGregor Coll.) ; and seven specimens E 23664-5 and E 238885-9 in the British
Museum (Natural History) (Chauvel Coll.).
Certain points of interest were seen in Mitrocystella incipiens incipiens from
Bohemia. Three of the specimens studied are in the British Museum (Natural
History) E 23606-8 and six in the Museum of Comparative Zoology, Harvard
(580-5). A large number are also preserved in the Narodni Museum (Prague), but
of these only one, in a siliceous nodule (Ace. cat. 22011, Inv. no. 688, Sarka Beds
(dy2), loc. Sarka, coll. Hanus) was informative.
GENERAL SHAPE AND PLATE NOMENCLATURE : The thecal skeleton of M. i. miloni
consists of two parts (Fig. I3a, b). There is a shield of large plates forming what
is here regarded as the dorsal side ("plastron" (Caster 1952), "face inferieure "
278
PRIMITIVE FOSSIL CHORDATES
I cm
FIG. 13. Mitrocystella incipiens miloni. a. dorsal ; b. ventral ; c. right ; d. anterior ;
e. posterior aspects, as = anterior stem ; bo = branchial opening ; ia = interossi-
cular articulation ; mo = mouth ; ng = narrow groove (lateral line) ; or = oral plate ;
ps = posterior stem ; std = styloid ; tr = transverse ridge ; vp = ventral plate of
posterior stem ; x = point where a ventral plate imbricates over a dorsal ossicle.
WITH ECHINODERM AFFINITIES
279
mo
bo
FIG.
280
PRIMITIVE FOSSIL CHORDATES
O
fi
WITH ECHINODERM AFFINITIES
281
FIG. i3d.
ng
FIG. 130.
(Chauvel 1941), " Dorsalseite " (Jaekel 1900), " Unterseite " (Jaekel 1918), " reverse
side " (Gislen 1930)). The ventral face (" carapace " (Caster 1952)) was evidently
more flexible except posteriorly.
The plates present in the theca are as follows:
Notation
M4L
M5L
MA
MSB
Name
Left dorsal ist marginal
Left ventral ist marginal
Left 2nd marginal
„ 3rd ,,
,, 4th
„ 5th
Anterior marginal
Right dorsal ist marginal
Right ventral ist marginal
,, 2nd marginal
„ 3rd
Chauvel 1941
M i° marginale droite
I + E Interbasale and epibasale
M2 2° marginale droite
M3
M4
M6
M
MI i° marginale gauche
I + E Interbasale and epibasale
M2' 2° marginale gauche
M3' 3°
1> V*
282 PRIMITIVE FOSSIL CHORDATES
Notation Name Chauvel 1941
M4R ,, 4th „ M/ 4°
MSB „ 5th „ M5' 5°
M6R „ 6th „ M6' 6°
CL Left central H2 2° hypocentrale
CA Anterior central H3 3°
CB, Right central Hx i°
Ventral plates epicentrales
VPM Median posterior ventral No special name
VPL Left posterior ventral
VPB, Right posterior ventral
Chauvel's scheme, and to a lesser extent the one adopted here, is based on that
of Jaekel (1918), with additions. The plates just anterior to the stem, i.e. MILV,
MILR, MILD and MIRD, must be homologous with the like-named plates in cornutes.
The homologies of the other plates are unclear, except that the marginals must be
broadly homologous with those of cornutes.
The stem is divided into anterior, medial and posterior parts as in the cornutes.
Details of the stem skeleton are given below (p. 289).
THECAL OPENINGS: The mouth (mo in Fig. I3b) faces slightly leftwards (cf. p.
314). It is bordered above by part of the rigid dorsal shield (Men, MA, MCL) and
below by about fifteen elongate oral plates (or). These are fixed to a flexible lower
lip, studded with post-oral plates, which is dorsal to the front edge of the ventral
armour.
The rigid skeleton above the mouth of M. i. miloni contrasts with the situation
in Cothurnocystis elizae where the skeleton was rigid beneath the mouth. An
intermediate situation exists in the earliest known mitrocystitid (Chinianocarpos
thorali Ubaghs from the Upper Tremadoc or Lower Arenig Series of the Montagne
Noire), where the mouth is entirely surrounded by large plates, i.e. MA dorsally,
MSB, and MSL ventrally (Ubaghs 19610. and personal observation).
There are no external branchial slits in M. i. miloni. Paired, external, branchial
openings (bo in Figs. I3b, c, I5H) seem to have existed, however, near the posterior
right- and left-hand corners of the theca. The roughly horizontal suture between
MID and MIV on each side is curved (Fig. 15!) as if to facilitate articulation (cf.
Fig. 7) about the length of the suture. When MIV, because of high pressure inside
the theca, rocked backwards on this suture, an opening would appear between it
and M2, and close again when MIV rocked forwards as the pressure fell. The opening
would thus behave as an outlet valve. It would be faced on both sides almost
entirely by the connective tissue of the middle layer of the skeleton (Fig. 15 H)
which would provide a seal like that round the branchial slits of C. curvata. The
nerve n3 (optic) ran just anterior to the opening while n4 ran just median to it. The
branchial openings rested on the substratum but the analogy of modern rays and
skates shows that they could have functioned in this position. M. mitra (p. 314)
had similar branchial openings which are in some ways easier to interpret.
WITH ECHINODERM AFFINITIES 283
There was no external anus in M. i. miloni, as discussed below (p. 287).
A narrow vertical groove on Mmv (ng in Fig. I3b, c ; PI. 4, fig. 9) is here regarded
as a rudimentary lateral line (cf . p. 307, below) . It sometimes has a short horizontal
groove across it (PI. 9, fig. 4).
THE CHAMBERS OF THE THECA: A direct picture of the chambers of the theca
(Fig. I4a, b) can be obtained from the internal cast, whose surface is traversed by
grooves which separate the original chambers and correspond to ridges on the
skeleton.
A groove (oblique groove), running from near the right side of the mouth to near
the left side of the stem, is the most notable feature of the dorsal side of the internal
cast. This groove (" sillon transversal " of Chauvel 1941) is not symmetrical in
section. For most of its length it is steeper to the right than to the left so that it
grossly separates a left, anterior, ventral chamber from a right, posterior, dorsal
chamber.
The oblique groove is here held to be broadly homologous with the pharyngo-
visceral line of Cotkurnocystis elizae. The chamber anterior and to the left of it
corresponds to the pharynx of C. elizae and is henceforth called the left pharyngeal
chamber. The chamber posterior to, and to the right of, the oblique groove is
broadly homologous with the anterior coelom of C. elizae, apart from some com-
plexities which are discussed below.
The oblique groove is flexuous and varies in strength. Anteriorly it bays out
to the right. For a short distance in the anterior part of this embayment the left
side of the groove is steeper than the right side (Fig. 15 A; P1.5, figs. 7, 9). Here,
therefore, the left pharyngeal chamber overlay the anterior coelom. In the middle
of the embayment the groove is shallow and symmetrical (Fig. 156 ; PI. 5, figs, i,
7, 9). In the posterior part of the embayment it deepens, has a rounded floor,
and is steeper to right than to left (Fig. 156). Behind the embayment the groove
sends out a median branch (mb in PL 9, fig. 2). This is triangular in section (Fig.
I5D), tapers posteriorly, and is largely hidden in the internal cast. For a short
distance behind and left of the separation of this median branch the oblique groove
again has a rounded floor and is symmetrical (Fig. 150 ; PI. 9, fig. 2) or has the
right side only a little steeper than the left. Behind this the floor of the groove
suddenly becomes angular (at point v in PI. 9, fig. 2), with the right side distinctly
steeper than the left (Fig. I5E). The depth, angularity and asymmetry of the
groove increase gradually backwards (Fig. I-5F). Posteriorly the oblique groove
gives rise to two other grooves. The left one of these runs backwards and then
vertically downwards while the other (" sillon pedonculaire " of Chauvel 1941) turns
to the right.
The anterior embayment and weakening of the oblique groove suggest an out-
pouching from the left pharyngeal chamber. This outpouching is henceforth called
the right pharyngeal chamber ; in ontogeny it must have pushed the anterior coelom
upwards and partly obliterated its lumen.
The median boundary of the right pharyngeal chamber is indicated anteriorly
by the median branch of the oblique groove and more posteriorly by a very weak
284
PRIMITIVE FOSSIL CHORDATES
H
Bucca! cavity
Pharynx
Rectum and oesophagus
Atria
. . V + +
•.*.'.; Primary antertor coelom + + + + Brain cavity and nerve canals
j Posterior coelom
Outline of theca
Plate boundaries on
external surface
Definite boundaries, visible dorsally
Definite boundaries, invisible dorsally
Inner edges of intercameral ridges
FIG. 14. M. i. miloni. Chambers of theca. a. dorsal ; b. posterior aspects, og =
oblique groove. A — A to G — G, H and I indicate planes of section used in Text-fig. 15.
Stipple is used here as in Text-figs. 4 and 10.
WITH ECHINODERM AFFINITIES
285
Canals from posterior face of posterior coelom
FIG. i4b.
groove (grp in PL 5, fig. i and PL 10, fig. i) running from the right side of the median
branch to a point just right of the stem. This groove is weak because it does not
correspond to any actual gap between chambers at the surface of the skeleton
(cf. Fig. I5E, F).
In ontogeny the left pharyngeal chamber evidently preceded the right pharyngeal
chamber, and it is therefore likely that the left gill slits preceded the right ones.
This is what happens in the ontogeny of amphioxus (Willey, 1894, p. 130 ff.).
The rounding of the floor of the oblique groove just behind and left of the median
branch may indicate that the oesophagus opened here into the left pharyngeal
chamber. There are two reasons for this supposition. Firstly, the exact form of
the internal cast (PL 9, fig. 2) suggests that some roughly cylindrical structure
was in contact with the skeleton here. Secondly, by analogy with tunicates, the
oesophagus should open into the pharynx in a median, dorsal position. Comparison
with tunicates is reasonable on account of the disposition of the rectum, as discussed
below.
The posterior coelom (pco) is delimited by the above-mentioned, right and left
posterior grooves arising from the oblique groove. These sweep round the posterior
coelom and meet ventrally.
The right posterior groove corresponds dorsally to Chauvel's " sillon pedoncu-
laire ". The dissection shown on PL 5, fig. 10, shows the oblique ridge (obr, i.e.
the skeletal filling of the oblique groove) curving round gradually into the ridge
filling this " sillon pedonculaire " (rpco). The exposed surface of the oblique ridge
in this dissection consists of skeleton deposited against the limiting membrane of
the left pharyngeal chamber. The exposed surface of the ridge (rpco) consists of
skeleton deposited against the limiting membrane of the posterior coelom. The
smooth connection between these two ridges in the dissection suggests that these
membranes were, in fact, one and the same. The same dissection also suggests
that the leftward limit of the posterior coelom (llpc), i.e. the left posterior groove
arising from the oblique groove, was a fold in this membrane increasing in sharpness
posteriorly. It follows that the posterior coelom became constricted off during
ontogeny from the left pharynx when left pharynx and anterior coelom were already
separate entities. This mode of origin of the posterior coelom is reminiscent of the
origin of an epicardium in a tunicate, and it is noteworthy that Berrill (1955 '• 101)
regarded epicardia as homologous with coeloms. The groove on the internal cast
286
PRIMITIVE FOSSIL CHORDATES
to the left of the posterior ceolom is almost interrupted, towards its ventral end, by
a bridge (rb in PI. 5, fig. 4) whose significance is discussed below.
Two further chambers (Fig. 143., b; ra in PI. 9, fig. i), situated right and left of
the posterior coelom, must represent atria, for they lie between the gill openings
and the presumed positions of the internal gill slits. The atria are distinctly un-
symmetrical and the right one touches the posterior coelom along its whole median
border. The left one, on the other hand, does not touch the posterior coelom,
from which it is separated by a vertical hemicylindrical ridge (rr in PI. 5, fig. 4)
on the internal mould. This ridge connects ventrally with the bridge (rb) across
FIG. 15. M. i. miloni. Sections through theca to show disposition of membranes limiting
chambers, and other features of the soft anatomy, bo = branchial opening.
WITH ECHINODERM AFFINITIES
287
the groove to the left of the posterior coelom. Both atria are delimited dorsally
in some specimens by weak, horizontal grooves on the internal mould.
By analogy with Cothurnocystis elizae and C. curvata the rectum probably left
the posterior coelom near the ventral, left posterior corner of the latter, i.e. by the
bridge rb. Again by analogy with C. elizae and C. curvata, the rectum then ran
vertically upwards, i.e. along the ridge rr, and must then have opened into the left
atrium. Faeces would be washed away by the current through the left gill slits
almost exactly as in C. elizae and C. curvata, and would finally leave the theca
through the left gill opening.
skeleton -posterior coelom
nerve — — oesophagus & rectum
connective tissue & muscle
— pharynx
— buccal cavity — — atria
anterior coelom
FIG. 15, F-I.
288 PRIMITIVE FOSSIL CHORDATES
In a similar way the rectum of a tunicate tadpole either opens into the left atrium,
or its closed end touches the left atrium, to open there after metamorphosis (Fig.
16; Julin 1904; Grave 1921, 1944; Kowalevsky 1867, 1871; Garstang 1928).
The existence of a buccal cavity shows clearly on the internal moulds of several
specimens (be, PI. 5, fig. 7) just left of the mouth, where it evidently touched the
dorsal skeleton (MSL). Its wall was lightly calcified near the contact with the
dorsal skeleton and can be followed by dissection a short way into the internal
cast (PI. 5, fig. 9). No similar structure can be found right of the mouth where
the buccal cavity was probably separated from the skeleton by the pharynx and
anterior coelom (Fig. I5A). The broad shape of the internal mould is the same,
however, suggesting that the buccal cavity affected the dorsal skeleton without
actually touching it. The relationship of the oblique groove with the buccal cavity
la ato oes
st
«P iht
FIG. 1 6. Alimentary canal of the tadpole larva of the tunicate Clavelina rissoana, left
aspect, redrawn after Julin (1904, fig. 12). ato = atrial opening ; be = buccal cavity ;
bs = branchial slit ; ep = epicardium ; int = intestine ; la = left atrium ; mo =
mouth ; oes = oesophagus ; ph = pharynx ; st = stomach ; t = tail.
of M. i. miloni is almost exactly like that of the pharyngo-visceral line and buccal
cavity of C. elizae.
The thecal chambers of M. i. miloni and Cothurnocystis elizae were, therefore,
basically the same. The most fundamental difference is the appearance in M. i.
miloni of the right pharyngeal chamber, which pouched out from the primary or
left pharyngeal chamber towards the posterior, right-hand corner of the theca.
In so doing, the right pharyngeal chamber lifted the anterior coelom off the floor
of the theca and partly obliterated its lumen. For this reason, the junction between
anterior coelom and the left or primary pharyngeal chamber (oblique groove of
mitrates; pharyngo-visceral line of cornutes), which runs in both cornutes and mi-
trates from right of the buccal cavity to left of the stem, is in mitrates fixed to the
ceiling of the theca, instead of to the right, posterior side wall. Indeed, for much
of its length in M. i. miloni it traverses a central plate, i.e. its course is across MILD,
CR, MSR and MGR. It is interesting to note, therefore, that in the earliest known
mitrocystitid, Chinianocarpos thorali, the oblique groove likewise runs across the
ceiling of the theca, much as in M. i. miloni (Ubaghs 19610, and personal observa-
tion). In addition, variations in its depth and direction in C. thorali indicate that
the right pharyngeal chamber already existed. On the other hand, as in C. elizae,
WITH ECHINODERM AFFINITIES 289
the roof of the left pharyngeal chamber is a flexible integument and the oblique
groove is entirely borne on marginal plates (MILD and IVLut). It is as if, in
phylogeny, the oblique groove of C. thorali had been carried forwards and leftwards
by dorsal extensions of the posterior right-hand marginals.
The basically similar disposition of the chambers of the theca in mitrates and
cornutes strongly indicates, contrary to most previous authors, that the big-plated
side of mitrates corresponds to the dorsal side of cornutes and was uppermost in life.
Two objections to this orientation need to be dealt with. Firstly, in the earliest
known lagynocystid mitrate, Peltocystis cornuta Thoral from the Upper Tremadoc
or Lower Arenig Series of the Montagne Noire, the oblique groove sometimes runs
from anterior left to posterior right. This is a most abnormal occurrence among
mitrates, however, and is unknown in Mitrocystitidae and so can be disregarded.
Secondly, if the strut of cornutes were homologous with the ridge filling the oblique
groove of mitrates, orientation with the big-plated side downwards would be implied.
Such a homology is most unlikely. The strut does not resemble an intercameral
ridge, and was probably a purely mechanical feature (p. 258) that lost its function
and disappeared when one face of the animal came to be built of big plates. If
the strut were homologous with the oblique ridge there would be no homologue in
mitrates for the pharyngo- visceral line.
In summary, therefore, the chambers of the theca of M. i. miloni consisted of
buccal cavity, left pharyngeal chamber, right pharyngeal chamber, anterior coelom,
posterior coelom and left and right atria. In ontogeny the left pharyngeal chamber
must have been separate from the anterior coelom from a very early stage. The
right pharyngeal chamber certainly, and the posterior coelom probably, arose as
outpouchings from the left pharyngeal chamber. The rectum opened into the left
atrium as in a tunicate tadpole. Left gill slits probably preceded right gill slits in
ontogeny as in amphioxus. In its probable origin from the pharynx, the posterior
coelom can be compared with a tunicate epicardium. The oesophagus probably
opened into the left pharyngeal chamber near the junction with the right pharyngeal
chamber. It was the big-plated side of M. i. miloni that was uppermost and corres-
ponded to the dorsal side of a cornute. Finally, the earliest-known mitrocystitid
was in some ways transitional, in the arrangement of its chambers as in other
respects, between cornute and mitrate conditions.
THE STEM: The posterior stem of M. i. miloni consists of about fifteen segments
and ends abruptly. Each segment contains a dorsal ossicle (do in Fig. ijb) and
paired ventral plates (vp). Successive dorsal ossicles articulate with each other
at inter-ossicular articulations (iaf in Fig. iyb) which would have allowed vertical
flexing.
The precise mode of imbrication of plates and ossicles is important (Fig. 18).
Dorsal to the interossicular articulation the back of each ossicle overlaps the front
of the one behind. Similarly, the back of each pair of ventral plates overlaps the
front of the pair behind. The lateral, ventral margins of a dorsal ossicle overlap
the upper margins of the ventral plates of the same segment. But, certainly in
M. barrandei (at x in PI. 6, figs. 3, 5) and probably in M. i. miloni in the uncrushed
condition (PI. 5, fig. 5 at point x), the posterior, upper corners of a ventral pair
GEOL. 16, 6. 28
2QO
PRIMITIVE FOSSIL CHORDATES
do
gap
mqno prgp /poqp
mgne
\
FIG. 17. M. i. miloni. Reconstruction of the skeleton of a posterior stem segment,
a. anterior aspect; b. sagittal section; c. ventral; d. posterior aspect, aig = anterior
ossicular groove ; aiid = anterior inner, interossicular depression ; die — dorsal longi-
tudinal canal ; do = dorsal ossicle ; gap = ganglionic pit ; gapr = ganglionic process ;
iaf = interossicular articular facet ; mg = median groove ; mgne = median groove
(neural) ; mgno = median groove (notochordal) ; pig = posterior interossicular
groove ; piid = posterior inner interossicular depression ; pagp = postganglionic
process ; poid = posterior outer interossicular depression ; prgp = preganglionic
process ; vp = ventral plate.
WITH ECHINODERM AFFINITIES
291
die
FIG. iyd.
of plates embrace the lower front corners of the next dorsal ossicle behind. A similar
imbrication pattern, but with the ventral plates overlapping the dorsal ossicle
behind still more extensively, also exists in Chinianocarpos thorali (Ubaghs 19610,
fig. lE, and personal observation) .
According to Prof. Ubaghs' interpretation (19616) the ventral stem plates of
mitrates, which he homologizes with the dorsal stem plates of cornutes, were cover
plates capable of opening outwards, and the whole stem was an arm. It is clear
that the imbrication just described is very ill-suited to allow the ventral plates to
open outwards and, like the detailed stem structure of Cothurnocystis curvata
(p. 276), argues against Prof. Ubaghs' interpretation. It is also clear that Prof.
Ubaghs must be mistaken if, as here maintained, the massive posterior stem
ossicles were dorsal in mitrates and ventral in cornutes, for in neither case can the
sculpture on their internal surfaces correspond to the outside of a water-vascular
system.
The internal sculpture of the posterior stem ossicles is very complicated (Fig. 17,
18 ; PL 6, figs. 10, ii ; PI. 7, fig. 5). Above the articulations each ossicle is excavate
at back and front, with posterior and anterior, inner and outer depressions (aiid,
aoid, piid, poid). Also, in the median plane, there are anterior and posterior inter-
ossicular grooves (aig and pig) which connect with a dorsal, longitudinal canal (die)
perforating the ossicle. On the ventral surface of the more anterior ossicles there
is a broad, median groove (mg) which becomes progressively deeper posteriorly
in the stem till it passes, in the most posterior ossicles, into a median canal (me in
PI. 6, fig. 5). In each ossicle the median groove or canal gives rise to paired pits
(gap). Each pit is excavated in the ventral surface of a process (gapr) which
bifurcates outwards into two prongs (prgp anteriorly and pogp posteriorly). On
2Q2
PRIMITIVE FOSSIL CHORDATES
each side of the median groove, in the ventral surface of the ossicle, are lateral
grooves (Ig). Sometimes the lateral grooves are deepest over the processes gapr
(Fig. iyc; PI. 6, fig. 5). Sometimes, on the other hand, the lateral grooves are filled
with skeleton dorsal to those processes, in which case the natural moulds of the
pits on gapr are visible dorsally (PL 6, fig. 10 ; PI. 7, fig. 4).
The structure of the median groove or canal is highly significant. The groove
or canal seems to have enclosed two longitudinal soft structures. The first of these
was broadly cylindrical and determined the fundamental shape of the groove or
canal. It came in actual contact with the parts of the groove marked mgno in
Fig. ryb, c. The second structure was thin and strap-like and coated part of the
dnc
not
Ibv
FIG. 18. M. i. miloni. Block diagram of posterior stem, dlv = dorsal longitudinal
vessel ; dnc = dorsal nerve cord ; idm = inner dorsal muscle ; iv — interossicular
vessel ; Ibv = lateral blood vessel ; Iga — lateral ganglion ; not — notochord ; nv =
notochordal vessel ; odm = outer dorsal muscle ; vm = ventral muscle.
dorsal surface of the first structure. It occupied the parts of the groove marked
mgne in Fig. I7b, c and sent out lateral projections to the cups of the processes
gap. Natural moulds of the median groove, giving a representation in rock of the
original soft structures, are shown in PL 6, fig. 10 and PL 7, fig. 2. The more dorsal
structure became narrower, thinner and less evident posteriorly.
As regards interpretation, the broad cylindrical structure in the median groove,
by analogy with crinoids, was the chambered organ. Being an anti-compressional
structure it was placed at the level of the interossicular articulations, in the principal
axis of the stem, which would not shorten or lengthen on bending. Again by analogy
WITH ECHINODERM AFFINITIES 293
with crinoids, the structure coating the chambered organ would be the peduncular
nerve. Its nervous nature is consistent with its strap-like shape and with the
way it communicates with the cups of the processes gap (ganglionar processes),
for such cups could well contain ganglia. The peduncular nerve of M. i. miloni
therefore rested on the dorsal surface of the chambered organ, or, in chordate terms,
the dorsal nerve cord rested on the dorsal surface of the notochord. It is note-
worthy that the dorsal nerve cord rests directly on the notochord in tunicate tadpoles,
amphioxus, Agnatha and the embryos of other vertebrates, and also in myxinoids
and petromyzontoids it has, as in M . i. miloni, a distinctly strap-like shape. The
paired segmental ganglia of M. i. miloni can be compared with those in the tail of
appendicularians (Martini 1909). There is no trace of separate dorsal and ventral
spinal nerve roots. The nervous and other soft structures of the posterior stem
of M. i. miloni are reconstructed in Fig. 18.
Turning now to the musculature, the posterior stem could either flex ventrally
or stick out straight, as indicated by the interossicular articulations and imbricating
ventral plates. This is confirmed by fossils evidently preserved in the position of
death. PI. 6, figs. 3, 6 (M. barrandei) ; PI. 7, fig. 5 (M. incipiens incipiens) and PI. 5,
fig. 5 (M. i. miloni) show straight posterior stems or portions of them. Conversely,
PL 10, fig. 2 (M. i. miloni) shows the stem bent ventrally in the normal position of
preservation for the subspecies. Muscles would therefore be needed on at least
one side of the articulations, i.e. either dorsally or ventrally, and muscles or ligaments
on the other side.
It seems likely that the space between dorsal ossicles and ventral plates was
largely filled with muscle. The opposing muscles or ligaments must have been
sited in the interossicular depressions. The inner interossicular depressions are
very deep and therefore probably contained muscle. The outer interossicular
depressions may have contained ligament, or a different sort of muscle. The
structure (probably a blood vessel) filling the interossicular grooves probably
separated right and left muscle blocks in the interossicular depressions. Repetition
of interossicular depressions indicates serial repetition of dorsal muscle blocks.
The ventral muscles were probably also segmented, with the muscle blocks
situated between the ganglia. The divisions between muscle blocks are indicated
by: i. the above-mentioned skeletal infilling that sometimes interrupts the lateral
grooves dorsal to the ganglionar processes; and 2. the occasional presence of faint
ridges on the ventral surface of the ossicle, or grooves in the internal mould, which
point downwards and backwards (gmb in PI. 7, fig. 5) and whose upper ends coincide
in position with the ganglia.
The blood system of the posterior stem is difficult to reconstruct. It probably
included: i. a dorsal longitudinal vessel (dlv), occupying the dorsal longitudinal
canal; 2. interossicular vessels (iv in Fig. 18), occupying anterior and posterior
interossicular grooves; 3. transverse vessels, connected with the sides of the noto-
chord (Ibv in PI. 9, fig. 3) ventral to the segmental ganglia; and 4. a notochordal
vessel running down the middle of the notochord.
The evidence that the interossicular grooves carried blood vessels is that: i.
although they emerge from the notochord through the dorsal nerve cord, they seem
294 PRIMITIVE FOSSIL CHORDATES
to be too wide to have carried only an upward extension of the nerve cord, so far
as the thickness of the nerve cord can be judged from the form of the median groove;
2. the dorsal muscles would need a blood supply. In the mitrate Lagynocystis
Pyramidalis interossicular depressions for dorsal muscle and interossicular grooves
were present (personal observation) but there was no dorsal longitudinal canal.
In this form, therefore, the dorsal muscles must have been supplied with blood
up the interossicular grooves. By analogy it is therefore likely that the interos-
sicular grooves of M. i. miloni also carried a blood vessel.
The existence of a vessel down the middle of the notochord is not certain, but is
suggested by the following pieces of evidence: i. The crinoids have such a vessel
(haemal strand) ; 2. The interossicular and transverse vessels, which are joined
to the notochord, could well have connected with a notochordal vessel. At the
least, they indicate extensive vascularization inside the notochord; 3. There was
probably no longitudinal vessel ventral to the notochord in M. i. miloni since none
could have existed in cornutes, and no vessels which could have come directly from
a ventral longitudinal vessel are seen to connect with the ventral side of the noto-
chord when this is enclosed by skeleton (PI. 9, fig. 3); 4. L. pyramidalis lacked a
dorsal longitudinal vessel. Assuming, for the reasons given under (3), that this
form also lacked a ventral longitudinal vessel, then a notochordal vessel must have
existed. In such a fundamental feature M. i. miloni would probably resemble
L. Pyramidalis.
In summary, the posterior stem of M. i. miloni certainly had a notochord, a dorsal
nerve cord giving rise to paired, segmental ganglia, and segmentally repeated muscle
blocks. The vascular system included a dorsal longitudinal vessel, interossicular
vessels that left the notochord through the dorsal nerve cord, transverse vessels,
and probably a longitudinal vessel inside the notochord. The dorsal nerve cord
resting directly on the notochord is a prime chordate feature. The vascular system,
so far as can be worked out, seems to have been more like that of a crinoid.
The medial stem of M. i. miloni much resembles two posterior stem segments
(std in Fig. I3a) with the dorsal ossicles fused to form what is known as a styloid
(Jaekel 1918). The posterior surface of the styloid is very much like that of a
normal dorsal ossicle (PI. 7, fig. 3) with inner and outer, posterior interossicular
depressions (piid, poid), interossicular articulations and posterior, interossicular
groove (pig). The most obvious difference from a normal dorsal ossicle is that the
dorsal longitudinal canal turns sharply upwards anteriorly. The interossicular
grooves between the two segments of the styloid fuse to form an interossicular
canal (ic) which presumably ran upwards to join the dorsal longitudinal canal.
Neither the middle part of the dorsal longitudinal canal of the styloid, nor the
dorsal part of the interossicular canal have been seen, however. The anterior
surface of the styloid carries a broad lumen (als in PL 6, fig. 12), presumably serially
homologous with anterior inner and outer interossicular depressions of a posterior
stem ossicle. The dorsal longitudinal canal entered this lumen dorsally. A vertical
groove (vgls of PI. 6, fig. 12) posteriorly must be serially homologous with the
anterior, interossicular grooves. The lateral grooves (Ig) of the styloid produce
a serrated internal mould with the deepest parts of the groove dorsal to the seg-
WITH ECHINODERM AFFINITIES 295
mented ganglia. The median groove differs little from that of the posterior stem
ossicles.
The anterior stem is usually poorly preserved but probably contains about ten
segments. The skeleton of each segment consists of four plates (left, dorsal and
ventral, and right, dorsal and ventral) round a broad lumen. In M. barrandei
(PL 6, figs. 3, 5) the anterior stem could certainly flex upwards so as to lift the
posterior stem; this was presumably also possible in M. i. miloni. By analogy
with Mitrocystites mitra (p. 322) the anterior stem of M. i. miloni could probably
also flex sideways. In order to flex without telescoping, a median, anti-compres-
sional structure would be needed, i.e. a chambered organ or notochord. There
must also have been muscles, probably divided into segmental blocks, a dorsal
nerve cord, segmental nerves and a longitudinal blood vessel or vessels.
The reason why the massive ossicles of the posterior stem of mitrates were dorsal,
whereas those of cornutes were ventral, is almost certainly functional. The posterior
stem of cornutes was adapted for flexing upwards and the necessary shortening of
the dorsal side was made possible by a series of imbricating plates. The posterior
stem of mitrates was adapted for flexing downwards and the imbricating plates
are therefore ventral, while the articulations between the massive dorsal ossicles
prevented shortening along the principal axis.
Chinianocarpos thorali, as in other features, is transitional in the posterior stem
structure from the cornute condition. Like all other mitrates it has an imbricating
series of plates ventrally and a series of articulated ossicles dorsally, so that the
stem must have been able to flex downwards. However, the ossicles are relatively
less massive than in M. i. miloni and Mitrocystites mitra, and the ventral plates
relatively larger. Also, in the only two specimens of C. thorali where the posterior
stem is known (personal observation and Ubaghs 19610, Fig. iD, E) the posterior
stem definitely curves gently upwards.
The actual transition between cornutes and mitrates must have had neither
styloid nor stylocone, but simply two segments like those of the posterior stem,
articulated with each other so that they could bend either up or down. The re-
development of a solid element in the medial stem, preventing the anterior stem
muscles from pulling against the posterior ones, would be highly advantageous.
THE BRAIN AND CRANIAL NERVES: The brain and cranial nerves of M. i. miloni
can be reconstructed in detail (Fig. iga, b, c) partly because they were extensively
enclosed by skeleton, and partly because, when nerves ran in soft-tissue-filled spaces
in the skeleton, their exact positions can often be determined. Thus, in the posterior
ventral skeleton, the nerves ran in an extensive, median, soft layer (Fig. I5F, G,
H, I), presumably consisting of connective tissue, between a thin inner and a thick
outer layer of calcite. The positions of the nerves are indicated by dilatations of
the soft layer. These dilatations are flanked by flat-topped thickenings of the outer
layer (tol in PL 5, fig. 8), and often roofed over by gentle folds in the inner layer
(as in PL 5, fig. n). The inner layer of calcite is absent from the median and
anterior, more flexible parts of the ventral skeleton, and the connective tissue
layer, if it existed in this region, cannot be recognized.
Upward extensions from the median layer of the ventral skeleton entered the
2g6 PRIMITIVE FOSSIL CHORDATES
dorsal skeleton near the posterior right and left corners of the theca (Fig. 15!)
and there remained separate from the thecal cavity because of an inner layer of
calcite. More anteriorly and laterally other extensions from the median soft layer
of the ventral skeleton touched the inner face of the dorsal skeleton which was
excavated to receive them (Fig. I5F, G, H; si in PI. 7, fig. 6), but these extensions
were not separated from the thecal cavity by an inner layer of calcite.
In addition to these direct upward extensions of the ventral median layer, the
dorsal skeleton contained an extensive irregular system of spaces in the calcite.
These spaces must have been filled with soft tissue and are particularly evident
across sutures (e.g. si in PL 6, fig. 7).
The histological origin of the soft-tissue-filled spaces could not be studied, in the
absence of material showing actual stereom mesh. Resorption of calcite may have
played a part in their origin, but of this there is no proof. The presence of casts
of a calcite cleavage network (ccc in PL 5, fig. 2; PL 6, fig. 7) is the only direct
indication that the hard skeleton was calcite.
The nervous nature of the structures here called nerves, which was already
recognised by their discoverer Chauvel (1941), is virtually certain because: I. like
the aboral nerves of crinoids they radiate from the region where the stem joins
the theca; and 2. they often had a very compressed cross section (Fig. I5F, G; PL 5,
figs. 6, 8, n).
The brain, as in cornutes, was lodged in the theca, just in front of the stem. The
encephalic mould is divided into anterior (ap), medial (mp) and posterior (pp)
parts (Fig. iQa-c ; PL 6, figs, i, 4). The anterior part is frond-shaped and developed
along the posterior, median, dorsal suture (MILD/MIRD)- The medial and posterior
parts, like the brain of cornutes, lie in a cerebral depression which, however, is
excavated in the dorsal instead of the ventral first marginals, i.e. MIL and RD instead
of MIL and RV- The side walls of the posterior part of the cerebral depression
received the most anterior plates of the stem. The medial part of the encephalic
cast is bounded ventrally by two hypocerebral processes (enclosing Imp in PL 6,
fig. 2 — M. barrandei) which almost, but not quite, meet at the mid-line. Above
these, the middle part of the encephalic cast communicates with the thecal cavity
by a medial part foramen (mpf in PL 6, fig. 4 and PL 6, fig. 2 — M. barrandei} through
which, by analogy with Mitrocystites mitra (p. 322), passed paired medial part
nerves (mpn). Ventral to the hypocerebral processes the thecal cavity communi-
cates with the lumen of the anterior stem. In M. barrandei (PL 6, fig. 2) and
FIG. 19. M. i. miloni. Reconstruction of brain and cranial nerves, a. dorsal aspect ;
b. anterior aspect of posterior part ; c. right aspect of left side, af = anterior furcation
of palmate complex ; ap = anterior part of brain ; be = buccal cavity ; csb — carrot-
shaped body (lateral-line ganglion) ; csbn = nerve to carrot-shaped body (nerve to
lateral-line ganglion) ; e — vestigial eye ; mp = medial part of brain ; mpn = medial
part nerves (bases of optic nerves) ; n0 = nerves emerging from posterior coelom
near midline ; nt to n5 = nerves of palmate complexes ; olo = olfactory openings ;
pal = palmar nerve ; pb = pyriform body ; pc — peripheral canal ; pf = posterior
furcation of palmate complex ; pp = posterior part of brain ; ppn = posterior part
nerve ; r = rectum.
WITH ECHINODERM AFFINITIES
297
olo
FIG. 19.
298
PRIMITIVE FOSSIL CHORDATES
ne
csbn
olo
ppnPP 'ap P/al c Pc
mpn
FIG. igc.
Mitrocystites mitra (PL 9, fig. 6) the part of the encephalic cast enclosed by the
hypocerebral processes is slightly swollen, so that a lower and an upper part of
the medial brain (Imp, ump) can be distinguished. There are paired structures
on the front of the posterior part of the encephalic cast, running towards the median
plane and downwards (posterior part nerves, ppn in PL 6, figs. 2, 4).
The main structures related to the cranial nerves are as follows :
i. Right and left palmate complexes, so called because each consists of a trunk
and five digitations. The proximal trunks (palmar nerve, pal in Fig. iga-c; PI.
5, figs. 6, 8; PL 7, fig. i) first show themselves where they touched the anterior
wall of the posterior coelom (PL 7, fig. i) and, for some reason, caused the wall to
calcify. The palmar nerves then entered the soft layer of the ventral skeleton
at the ventral, anterior corners of the posterior coelom. After a short distance
they divided into anterior and posterior furcations (af, pf in Fig. iga-c; PL 5, figs.
6, 8). Each anterior furcation gave rise to two nerves (n1} n2) and each posterior
WITH ECHINODERM AFFINITIES 299
furcation to three nerves (n3, n4, n5). The courses of these will be described when
their nature is considered (p. 305). The left palmar nerve (Fig. IQC), judging by
the trace that it left in the front wall of the posterior coelom, looped over the rectum
before entering the ventral skeleton.
2. Right and left peripheral canals (pc in Fig. iga-c; PI. 5, figs. 3, 6; PL 6, fig. 7).
These were spaces in the dorsal skeleton which were well developed on either side
posteriorly and the right one can be traced at least as far forward as the suture
M3/4R. Both canals probably ended shortly in front of this. Posteriorly they
they received nerves n4 and n5 of the palmate complexes.
3. Right and left " pyriform bodies " (pb in Fig. iga., b; PI. 5, fig. 6; PI. 6, fig. 4;
PI. 9, fig. i; PL 10, fig. 3) homologous with those of cornutes. These bodies lay
as if pressed against the front faces of the posterior part nerves, but were actually
separated from these by a thin layer of skeleton. They were totally enclosed in
cupules in MILD and v and MIRD and v, except for a slit-like opening on the median
side of each body.
4. A " carrot-shaped body " (csb in Fig. iga, b; PL 5, fig. 6; PL 9, fig. 4; PL 10,
fig. 3) just behind the right pyriform body. This underlay and communicated
with the narrow groove (ng) on the surface of MIRV It received a laterally com-
pressed nerve anteriorly (csbn in PL 10, fig. 3).
5. Right and left conical openings into the buccal cavity (olo in Fig. iga, c;
PL 5, figs. 7, 9).
6. Right and left nerves (n0) that entered the soft layer of the ventral skeleton
from the posterior coelom, near the mid-line (PL 5, fig. n), within the plate VPM-
It is interesting to compare the brain and cranial nerves of M. i. miloni with
those of cephalaspids (Figs. 20, 21), for the latter are the only early Agnatha where
these organs are known in detail. There is broad agreement that the brains of
these fish much resembled that of Petromyzon, but there is unfortunately much
difference of opinion as regards the cranial nerves.
The classical hypothesis of head segmentation has caused these differences of
opinion, and therefore demands a digression. The version of the hypothesis ex-
pounded by Goodrich (1918, 1930) has been particularly influential (see e.g. de
Beer 1937 : 15 ff. ; Young 1950 : 144 ff.) and can suitably be explained here.
According to Goodrich the branchial slits originally emerged between somites
serially homologous with those of the trunk. Also there were " premandibular "
and " mandibular " pairs of gill slits anterior to any now remaining, i.e. anterior
to the spiracles of gnathostomes or to the homologous first branchial slits of Agnatha.
Between the " mandibular " and " premandibular " pairs of gill slits lay the first
prootic or " premandibular " pair of somites. These were associated with the
trabeculae cranii, which represented the skeleton of an original " premandibular "
branchial arch. Between the " mandibular " and the spiracular pairs of gill slits
lay the second prootic or " mandibular " pair of somites, with which the mandibular
skeleton was associated — originally as a gill arch, little different from the arches
behind it. Between the spiracular and the first post-hyoidean gill slits lay the
paired spiracular somites associated with the hyoid arch. The innervation of all
interbranchial somites was supposed originally to have been like that of the trunk
300 PRIMITIVE FOSSIL CHORDATES
somites, with paired dorsal and ventral roots. The dorsal roots, however, would
have had a strong branchial component. Accordingly, the first prootic (" pre-
mandibular ") somites would have had the paired profundus branches of the tri-
geminal as their dorsal-root, branchial nerves, and would have had the oculo-motor
nerves as their ventral roots. The second pair of prootic (" mandibular ") somites
would have had the rest of the trigeminal complex as their dorsal-root, branchial
nerves, and the trochlear nerves as their ventral roots. The third pair of prootic
somites would have had the facial nerves as their dorsal-root, branchial nerves and
the abducens nerves as their ventral roots. The hypothetical ventral roots and
paired somites associated with the first post-hyoidean arch have supposedly dis-
appeared, but the glossopharyngeal nerves would have been the corresponding
dorsal-root, branchial nerves. Each of the dorsal-root nerves going to the first
few pairs of metotic somites supposedly had originally a branchial branch to the
" corresponding " gill slit, but these branchial branches have since bunched together
to form the paired vagus nerves. Consequently each metotic somite now has a
ventral and dorsal spinal root nerve and is also, in theory, related to a branchial
branch of the vagus. More detailed expositions of the hypothesis can be found
in the cited works of Goodrich, de Beer and Young.
In considering this hypothesis, it must first be emphasized that branchiomerism
and trunk segmentation are, of course, real phenomena. It is their supposed,
original, simple relationship which is in doubt, and which has not everywhere been
accepted (e.g. Romer 1949 : 555). Again, it is likely that the mandibular arch
represents an original branchial arch, serially homologous with those behind it
(e.g. Devillers 1958 : 573) and it is certain that the mandibular and maxillary
branches of the trigeminal nerves were the original innervation of the mandibular
and maxillary skeleton. It is very doubtful, however, that mandibular and pre-
mandibular gill slits ever existed, or that the trigeminal complex was originally
branchial. Finally, the prootic somites are real entities which give rise to the
oculo-motor muscles, and they are really innervated by the oculo-motor, trochlear
and abducens nerves. But the serial homology of the prootic somites with the
metotic somites or with the mesodermal pouches between the gill slits, the grouping
of their nerves as ventral roots corresponding to dorsal roots represented by pro-
fundus, " true " trigeminal and facial nerves, and the separation of the prootic
somites by hypothetical gill slits, are all baseless suppositions.
The arguments against the segmentation hypothesis in general, and Goodrich's
version of it in particular, were forcefully marshalled by Kingsbury (1926). His
case can be summarized as follows:
1. Gill slits seldom equal in number, and always appear later than and ventral
to, the divisions between the trunk somites of the same region, and in amphioxus
the gill slits do not even appear simultaneously on right and left sides. It may
be added that there is certainly no serial relationship whatever between gill slits
and trunk (i.e. tail) musculature in tunicate tadpoles.
2. The prootic somites differentiate, in general, from behind forwards, whereas
the metotic somites, their supposed serial homologues, differentiate from in front
backwards.
WITH ECHINODERM AFFINITIES 301
3. The nerves innervating the prootic somites, in particular the trochlear and
abducens, do not have the central relations expected for somatic motor nerves,
and do not pair with the profundus, " true " trigeminal and facial nerves as the
hypothesis would require. The trochlear, in particular, always comes off the brain
dorsally, after decussation of fibres.
4. The trigeminal nerves do not innervate gill slits in any living vertebrate.
5. The vagus nerve is never seen to be related to the spinal nerves in the way
that the hypothesis suggests is primitive. In addition, the intestinal branch of
the vagus will not fit into any segmental scheme. It may be added that the oldest-
known vagus nerves — those of cephalaspids — are similar in morphology to the
vagus nerves of living fish and agnathans.
Among recent works that adopt a segmentationist viewpoint, the contributions
of Jarvik (1954 : 71 ff.), Bertmar (1959, esp. p. 341 ff.), Stensio (1963, esp. p. 29 ff.)
and Tarlo & Whiting (1965) should be mentioned. It is fair to say that all
these authors, convinced that a segmentation scheme of Goodrich type was primitive,
have tried to make the structures that they saw fit into it. The results are fairly
plausible but not convincing enough to prove the truth of the scheme.
Jarvik, with great plausibility, serially homologised the elements of the mandi-
bular arch in the crossopterygian Eusthenopteron with the elements of the hyoid
arch and post-hyoidean arches behind. He also tried to recognise, but far less con-
vincingly, the skeletal elements of a premandibular arch, anterior to the mandibular
arch. Bertmar tried to do the same for certain Recent teleostean fishes. The
account given by Jarvik (1954 : 71) of the views of previous workers is most reveal-
ing. For when authors such as Holmgren, Jarvik, Jaekel, Severtsoff and Allis,
to name only some, disagree so completely, even as to the number of arches, it
seems doubtful if such arches exist.
Stensio (1963, esp. p. 29 ff.) elaborated the classical subdivision of the trigeminal
complex, and wrote of paired trigeminal I and paired trigeminal II which he held
to innervate mandibular and premandibular arches. Both pairs of trigeminals
were supposedly provided, in cephalaspids, with dorsal sensory and ventral bran-
chial branches. However, Stensio gave no evidence of the existence of the paired
dorsal branches of trigeminal II in cephalaspids (1963 : 29). Further, the inter-
pretation of the other trigeminal branches (profundus, maxillary and mandibular),
which careful reading shows to be identical to the interpretation of Wangsjo (1952),
is not the most natural that can be offered.
Tarlo & Whiting (1965) reinterpreted certain paired pits inside the head shield
of Cyathaspididae (Heterostraci) . They saw in them indications of a complete
series of head somites where previous authors had found indications of gill chambers.
They also regarded the first two pairs of the pits that they figured as showing the
positions of prootic somites. It is worth noting that Denison (1964 : 344) has, on
good grounds, denied the existence of the first of these pairs of pits. Central to the
argument of Tarlow & Whiting is the fact that the pits are sometimes striated
approximately transverse to their axes, i.e. sub-parallel to the long axis of the
animal. The authors therefore suggested that the striations cannot represent
gill lamellae as Stensio had suggested (1958 : 366) but must somehow be related
302
PRIMITIVE FOSSIL CHORDATES
to somites with fibres running parallel to the long axis of the animal. It is true
that gill lamellae cannot be transverse to the direction of flow of water through a
gill, but it is by no means obvious that the striations would be transverse to the
direction of flow in Cyathaspididae, if the pits were occupied by gill pouches.
Incidentally, the skeleton surrounding the gill chambers of Cephalaspididae shows
very similar striations (see e.g. Stensio 1958 : 197, fig. 115; 1963 : 33, fig. 16;
Wangsjo 1952 : 159, fig. 156). These also are roughly, though not accurately,
transverse to the length of the gill chambers, but are nevertheless parallel to the
likely direction of flow of water through the pharynx. In any case the distribution
of the striations in cephalaspids, beginning just behind the peripharyngeal bands
(Wangsjo, loc. cit.}, shows that, whether or not they represent gill lamellae, they
velr
IX
rm
FIG. 20. Anterior part of roof of oralo-branchial chamber of the cephalaspid Nectaspis
areolata Wangsjo. Redrawn after Wangsjo (1952, fig. 150), relabelled, be = buccal
cavity ; ibs^ 2 = interbranchial septum ; kx> 2 = branchial pouches ; velr = velar
ridge ; V, VII, IX trigeminal, facial and glossopharyngeal nerves.
must certainly show the positions of gills. It is likely that they had the same
significance in cyathaspidids. If interpreted as housing gill chambers, the first
pairs of pits that exist (the second pair of Tarlo & Whiting) is not so far forward
that it could not be homologous with the spiracular chambers of gnathostomes or
the first gill chambers of Agnatha. Also, even if the pits housed interbranchial
mesodermal pouches, as Tarlo & Whiting suggest, there is no sign that these pouches
would form a continuous series with the trunk somites. The pits always cease
just anterior to the branchial openings, and therefore well anterior to the back of
the head shield (Denison 1964 : 345).
Regarding cephalaspid cranial anatomy, there is a large oralo-branchial chamber
in the head shield (Fig. 20) which is divided into a right and left series of smaller
chambers. Stensio (1927, 1958, 1963) maintained that all these smaller chambers
carried branchial chambers. He also maintained (1927 : 167) that the division
between the first and second chambers may have carried the velum, so that the
first supposed pair of gill slits would be actually in front of the velum and would
comprise perforations in the wall of the stomodeum. According to Stensio the
buccal cavity would correspond only to a small area at the extreme front end of
the oralo-branchial cavity (dpr in e.g. Stensio 1927, fig. 36). Wangsjo (1952, esp.
WITH ECHINODERM AFFINITIES 303
pp. 154 ff.), on the other hand, contended that the first pair of chambers (be in
Fig. 20) represented the buccal cavity, that the ridge behind it (velr in Fig. 20)
supported the velum, as Stensio had thought, and that only the chambers behind
this ridge (kl, k2 in Fig. 20) were branchial. This second view is almost certainly
correct. The chambers making up the first pair are clearly different from the
chambers behind them (cf. Fig. 20, and e.g. Wangsjo 1952, fig. I5a, b, c). They lie
in front of the distinct median groove in the roof of the oralo-branchial chamber
made by the dorsal aorta. They never have the above-mentioned transverse
striations which sometimes occur on the other chambers, and which probably
indicate gills, and they never have any sign of branchial openings. Wangsjo
(1952 : 135) described grooves in the skeleton for peripharyngeal bands, within
the second pair of chambers, and the striations that indicate gills only occur behind
these peripharyngeal grooves. This is exactly parallel to the situation in tunicates,
amphioxus and ammocoete larvae. Further, Stensio's belief in gills anterior to
the velum is surprising from both hydrodynamic and comparative points of view,
since the velum functions basically as a valve upstream of the gill slits and never
has branchial slits anterior to it in any living chordate.
Stensio (1927, 1958) originally maintained that the first pair of chambers (i.e.
what is here interpreted as buccal cavity, be in Fig. 20) received the right and
left profundus branches of the trigeminal, which were thus branchial nerves. The
second pair (kx in Fig. 20) received the " true " trigeminal nerves — also branchial.
The third pair (k2) received the facial nerves, the fourth (k3) received the glosso-
pharyngeal nerves, and fifth and succeeding chambers received successive branches
of the vagus. His views, therefore, tallied well with classical segmentation theory.
Allis (1931) and Wangsjo (1952 : 63) disagreed with Stensio's original views.
They proposed instead that the profundus nerves were weakly developed and
ran up through the orbits to the dorsal side of the head. Allis and Wangsjo held
further that the nerves to the first pair of chambers (i.e. buccal cavity) were the
maxillary branches of the trigeminal and the nerves to the second pair of chambers
(i.e. first branchial chambers) were the mandibular branches of the trigeminal.
In support of this latter contention Wangsjo cited the absence of swellings that
might represent ganglia in the courses of these nerves to the first branchial chambers,
which supposedly showed that they were motor nerves like the mandibular trige-
minal nerves, but this argument is weak. Ganglia do not always show as obvious
swellings of the nerves (cf . e.g. the reconstruction of the cranial nerves of Petromyzon
by Johnston (1905, PI. 5) especially the proximal, ganglionar part of the facial
nerve) and still less as swellings in the nerve canals. As regards the nerves to
more posterior pairs of chambers, Allis and Wangsjo agreed with Stensio (1927).
As already mentioned, Stensio (1963 : 31) appears to have adopted Wangsjo's
interpretation of the nerves to the first two pairs of chambers and of the profundus
nerves.
A much more natural interpretation, however, was proposed by Lindstrom
(1949 : 445). His interpretation of the profundus nerves agrees with that of Allis,
Wangsjo and Stensio (1963), i.e. he thought that they were weak, and innervated
part of the dorsal surface of the head. For him, however, the paired nerves to the
3«4
PRIMITIVE FOSSIL CHORDATES
buccal cavity correspond to the whole of the rest of the trigeminal complex, since
this supplies the mouth region in living agnathans and fish. The nerves to the
first pair of branchial chambers were the facial nerves, for these supply the first
pair of branchial chambers of living agnathans and the homologous spiracles of
gnathostomatous fish. The nerves to the second pair of branchial chambers were
therefore the glossopharyngeal nerves, and the nerves to the third and succeeding
pairs of chambers were the branchial branches of the vagus. Lindstrom held that
sf,
sf,
sf.
Xbr,
FIG. 21. Ventral aspect of canals associated with brain and cranial nerves of the cephalas-
pid Nectaspis areolata Wangsjo. Ventral aspect, redrawn after Wangsjo (1952, fig. 12),
relabelled, gch = trigemino-lateralis chamber ; hys = hyphophysis ; orb = orbit ;
sf = sensory field canals ; vest = vestibule ; V = trigeminal, VII = facial, Xbrj_4 =
branchial branches of vagus.
the facial nerves left the brain anterior to the ear and ran through paired canals,
the proximal parts of which were labelled 1 by Stensio (1927 : 136, fig. 28). These
canals touched the orbits in parts of their courses (cf. Fig. 21). The glossopharyn-
geal, according to Lindstrom, left the brain just behind the ear through the paired
canals VIIIp of Stensio (1927, fig. 28), and ran through the vestibule on their
way to the second branchial chambers. Although, therefore, the points of origin
and the end organs of the facial and glossopharyngeal were the same as in modern
analogues, the intermediate courses of these nerves were somewhat different.
Lindstrom, however, points out that this is not surprising, since the most anterior
WITH ECHINODERM AFFINITIES 305
gill chambers of cephalaspids lay far forward relative to the brain, compared with
modern analogues. There is, indeed, every reason to accept Lindstrdm's interpre-
tation which has been followed in labelling (Figs. 20 and 21).
Other points have been at issue in cephalaspid cranial anatomy. Thus the large
paired chambers just behind the orbit (gch in Fig. 21) were regarded by Stensio
(1927) as myodomes for oculo-motor muscles. Wangs] 6 (1952 : 67 ff.) has shown
that sometimes they are fusiform in shape and cannot therefore be myodomes.
He identified them as chambers for the trigemino-profundus and anterior lateralis
ganglia, and there seems little doubt that he was right.
Again, the well-known dorsal and lateral fields of cephalaspids were regarded as
electric fields by Stensio (1927), but Bohlin (1941), Westoll (1945) and Wangsjo
(1952 : 192) thought they were sensory, largely on account of their thinness. They
connected the fields, with some doubt, to the lateralis system. Watson (1954 :
20 ff.) elaborated a somewhat similar interpretation, pointing out that the so-called
nerve canals (sf^g in Fig. 21) to the dorsal and lateral fields were much too wide
to have carried only nerves. He suggested instead that they carried canals from
the labyrinth and that the whole apparatus was a development of the ear that
substituted functionally for the deficient lateralis system. Stensio (1963 : 38)
accepted that the fields in question were sensory fields of a special nature.
The brain and cranial nerves of M . i. miloni will now be compared with those
of agnathans in general and cephalaspids in particular, assuming that the inter-
pretations of the latter shown in Fig. 20 and 21 are correct.
The brain (Figs, iga-c) resembles that of a lamprey or cephalaspid, except for
being much shorter. The posterior part (pp) corresponds to the medulla oblongata
plus the ventral part of the mesencephalon. The posterior part nerves (ppn) are
the medullary nerves, presumably including equivalents of everything from tri-
geminal V to vagus X. Oculo-motor nerves (III, IV, VI) would not be repre-
sented as such, for there could be no oculo-motor muscles (cf. Mitrocystites mitra
P- 319).
The medial part of the brain represents the optic lobes dorsally and the dience-
phalon more ventrally. The foramen (mpf) would be the outlet for the optic
nerves (mpn). The whole of the medial part of the brain dorsal to the optic nerves
would be optic in function. The part of the medial part of the brain just ventral
and posterior to the optic nerves would, on vertebrate analogies, be functionally
related to the hypophysis, which would have lain just beneath the gap between
left and right hypocerebral processes. This lower medial part of the brain (Imp),
in agreement with its different function, is differentiated from the optic, upper
medial part (ump), as mentioned above, by being slightly protuberant in Mitro-
cy stella barrandei and Mitrocystites mitra.
The anterior part of the brain (ap), which connected with the rest of the brain
just dorsal to the optic nerves, would represent the telencephalon, with an olfactory
function.
Turning to the palmate complexes, the anterior furcation (af) of each gave rise
to H! and n2 (Figs, iga-c; PI. 5, figs. 6, 8, n). The courses of these within the
median layer of the ventral skeleton, through most of MIL and BV, are flanked by
GEOL. 1 6, 6. 29
306 PRIMITIVE FOSSIL CHORDATES
thickenings of the outer calcite layer (see especially PI. 5, fig. 8). These thickenings
suddenly stop anteriorly, but the nerves must clearly have continued beyond them.
The nerves nx presumably ran forward and innervated the muscles inside the flexible
ventral skeleton. The nerves n2 presumably followed the lateral extensions of the
soft layer out of the ventral skeleton (Fig. I5E, F) and can be traced again, after
only a short interval, by means of right and left grooves in the skeleton corresponding
to a ridge each side of the internal cast (n2 in PL 5, fig. i). The ridges run forwards
into the buccal cavity (n2 entering be in PI. 5, figs. 7, 9).
The nerves n2 therefore compare at first sight with the nerves that innervate the
buccal cavity of cephalaspids, i.e. the right and left trigeminal V, but further con-
sideration refines this comparison. Thus Lindstrom. has shown (1949 : 354, 384,
439) that the trigeminal complex of modern agnatha has paired maxillary and
mandibular branches. The same may also have been true of cephalaspids, though
direct evidence would not be expected since the relevant parts of the anatomy
would be ventral to the dorsal shield. By comparison, therefore, it seems likely
that the nerves nx of M. i. miloni correspond to the mandibular, and n2 only to
the maxillary branches of the trigeminal. The probable motor function of the
nerves nx agrees with this supposition. The fact that the nerves n2 innervated
the ventral wall of the theca and the lower lip in Mitrocystites mitra (p. 322), and
probably did so in M. i. miloni, does not argue against comparing them with the
maxillary trigeminal nerves of cyclostomes, which behave similarly (Lindstrom
1949 : 439)-
The posterior furcations of the palmar nerves (pf in Fig. iga, PL 5, figs. 6, 8)
gave rise to nerves n3, n4 and n5 on each side. The positions of n3 are defined on
each side in the median soft layer of MIL and RV by thickenings of the outer calcite
layer. Their courses cannot be traced in the soft layer after the latter leaves the
ventral skeleton. The nerves n3 of M. i. miloni clearly correspond to n3 of Mitro-
cystites mitra (p. 322), for in both species they lay between the nerves n2 and the
branchial openings. The nerves n3 of M. mitra were clearly optic nerves leading
to eyes resting on the sutures M2/3R and L and n3 of M . i. miloni must be vestigial
optic nerves. In many specimens of M. i. miloni the soft-tissue filled cavities of
the dorsal skeleton flanking the sutures M2/3L and R show angular extensions (e in
Fig. iga-c; PL 5, fig. 3; PL 6, fig. i) in much the same position as the eyes of
M. mitra. These extensions may represent vestigial eyes.
Nerves n4 and n5 from the posterior furcations (Fig. iga-c; PL 5, figs. 6, 8) can
be followed through the median layer of MIL and RV and into the posterior, dorsal
extensions of this layer in MIL and RD where, ultimately, they join the peripheral
canals (pc in Figs, iga-c; PL 5, figs. 3, 6; PL 6, figs, i, 7). In both ventral and
dorsal skeleton, their courses are flanked by thickenings of the outer layer of calcite.
Nerves n4 and n5 are on each side median and posterior to the gill opening and
cannot therefore be homologous with any part of the trigeminal complex of an
agnathan or fish.
The peripheral canals, judging by their superficial position, were probably sensory,
and n4 and n5 represent their nerve supply. It is possible that the peripheral
canals are homologous to the sensory fields of cephalaspids, but equally possible
WITH ECHINODERM AFFINITIES 307
that any resemblance is convergent. The possible homology would be inconsistent
with the above-mentioned suggestions of Bohlin (1941), Westoll (1945) and Wangsjo
(1942 : 192) that the sensory fields of cephalaspids might be related to the lateralis
system, since in M. i. incipiens the lateralis system exists in a very primitive form
(see below) and is not related to the peripheral canals. It would also be inconsistent
with Watson's (1954) interpretation of these fields as elaborations of the ears, since
the lateralis system of M. i. miloni was too primitive to include ears.
The palmar nerves, to judge by what comes off them peripherally, must have
formed proximally by fusion of medullary nerves (posterior part nerves) and optic
nerves (medial part nerves). This is reasonable since in M. i. miloni, M. barrandei
and Mitrocystites mitra the posterior part nerves ran forwards, downwards and
admedian, and in M. mitra direct evidence shows that the medial part nerves ran
forwards, downwards and away from the median plane. They could, therefore,
easily have fused shortly after leaving the dorsal skeleton.
The nature of the pyriform bodies, the carrot-shaped body behind the right
pyriform body, and the narrow groove (ng) in MIRV must be considered together.
The pyriform bodies are reminiscent of the trigemino-lateralis chambers of cephal-
aspids (gch in Fig. 21) in position and their shape suggests that they carried ganglia.
As mentioned above, however, Wangsjo (1952 : 67) has shown that the trigemino-
lateralis chambers in cephalaspids carried both the trigemino-profundus and anterior
lateralis ganglia. Bearing this in mind, it seems likely that the pyriform bodies
correspond to trigemino-profundus ganglia alone, that the carrot-shaped body was
a lateralis ganglion, that the groove that it underlay was the lateral line and
that the canal emerging from the front of the body (csbn) carried a lateral-line
nerve.
Several considerations support this view. Firstly, the right and left trigemino-
profundus ganglia of Petromyzon lie just in front of the anterior lateralis ganglia,
just as the right pyriform body lies just in front of the carrot-shaped body. Secondly,
lateral-line ganglia are often peripheral in position. And thirdly, Pumphrey (1950)
has shown that the acustico-lateralis system, on physiological grounds, must first
have appeared as lateral-line.
As regards functioning, the groove (ng) of M. i. miloni, because of its position,
would often be buried in mud, but this would not affect its efficiency as lateral-line,
since the damping effect of half a centimetre of mud would be negligible. Pumphrey
has shown (1950 : 7) that the great length of the lateral line in fish makes it possible
to locate the position of sound sources. It is therefore interesting that in Chiniano-
carpos thorali the groove (ng) is represented only by a pit (personal observation)
so that the system increased in length during the evolution of the Mitrocystitidae.
Comparison of the olfactory nerves and telencephalon with cephalaspids is of little
help, since the olfactory opening of these fish lay on top of the head between the
eyes. This is a highly unusual feature among vertebrates and corresponds to
nothing in the mitrocystitids. A more helpful comparison is with Heterostraci.
It is generally accepted that a right and left nasal sac opened downwards into the
buccal cavity in these fish. Stensio (1958) opposed this view, but Heintz (1962)
argued convincingly in favour of it and refuted Stensio's reconstructions.
3o8
PRIMITIVE FOSSIL CHORDATES
It seems likely that the apices of the conical pits (olo) that open into the buccal
cavity in M. i. miloni represent the points where the olfactory nerves entered the
skeleton. The conical pits may themselves represent the nasal sacs of Heterostraci,
but it is perhaps more likely that olfactory sensitivity was distributed over the
whole dorsal wall of the buccal cavity, and the conical pits were simply the places
where olfactory fibres converged before entering the skeleton.
The cavity containing the anterior part of the brain (ap) had numerous conical
extensions to right and left. These extensions probably represent the places where
olfactory fibres, or bundles of fibres, left the skeleton. The course of these fibres
between the olfactory openings (olo) and the anterior part of the brain is conjectural.
They may have passed through the short canals (sc) across M2/3L and R, shown in
PL 6, fig. 7, but, being very thin structures, they would not normally be traceable.
The olfactory system of M. i. miloni, in any case, compares closely with that of
Heterostraci except that the brain and olfactory sense organs were widely separated.
It is almost certain that the viscera, and very likely the gill slits, would need to
be innervated from the brain in M. i. miloni. By comparison with vertebrates in
general the corresponding nerves would be respectively the paired intestinal branches
of the vagus, and the branchial branches of the facial, glossopharyngeal and vagus
nerves, all of which, of course, arise from the medulla. With one likely exception
there is no direct evidence of these nerves in M. i. miloni, but they could well have
existed without touching the skeleton. The exception corresponds to the paired
nerves n0 to the ventral skeleton, which, by comparison with Petromyzon (Johnston
1905, pi. 5) may possibly represent the non-lateralis component of the hyomandi-
vn
ato
FIG. 22. Brain and associated structures of the tadpole larva of the tunicate Amaroucium
constellatum (Verrill) (redrawn after Grave, 1921, fig. C). ato = atrial opening ; dnc =
dorsal nerve cord ; ga = definitive ganglion ; hys = hypophysis ; mo = mouth ;
not = notochord ; sng = subneural gland ; sv = sensory vesicle ; vga = visceral
ganglion ; vn = visceral nerve.
WITH ECHINODERM AFFINITIES 309
bular branches of the facial. It is possible that the nerves n0 also represent the
median-line nerves of cornutes.
The hypophysis of M. i. miloni must, as already mentioned, have underlain the
lower medial part of the brain (Imp) and have been connected to the buccal cavity
by a duct, as it is in tunicates. In echinoderm terms it corresponds in position to
the axial sinus plus the water vascular system, i.e. organs arising from the left axo-
hydrocoel. The opening into the buccal cavity would correspond to the hydropore.
The possibility of this homology was implied by Goodrich (1917).
It is interesting to compare the brain of M. i. miloni with that of a tunicate
tadpole such as Amaroucium constellatum as described by Grave (1921) (cf. Fig.
22). This has a visceral ganglion posteriorly, which joins the dorsal nerve cord.
Anteriorly are the sensory vesicle to the right, containing the eye and the statocyst,
and the definitive ganglion to the left, in contact with the hypophyseal duct. A
visceral nerve runs from the left, anterior corner of the visceral ganglion to the
region in front of the oral siphon.
The visceral ganglion of a tunicate tadpole can be compared with the medulla
oblongata of vertebrates and the posterior part of the brain of M. i. miloni. The
visceral nerve corresponds in general to the nerves arising from the medulla, and
therefore to the posterior part nerves. The sensory vesicle corresponds to the optic
lobes, the optic part of the diencephalon, the optic nerves and the eyes of a verte-
brate, and to the upper medial part of the brain, optic nerves (n3) and eyes of M . i.
miloni. The definitive ganglion corresponds to the hypophyseal part of the dien-
cephalon of a vertebrate, and therefore to the lower medial part of the brain of
M. i. miloni. Perhaps the most important differences in the nervous systems of
tunicate larvae on the one hand, and vertebrates and mitrocystitids on the other,
are the absence in tunicate tadpoles of telencephalon, olfactory nerves and acustico-
lateralis system. These differences could easily be due to very small size. The
statocyst is likely to be a specialization peculiar to tunicates, and functionally
equivalent to the acustico-lateralis system.
In further connection with the optic system Dilly (1964) showed that the outer
segments of the visual cells of tunicate tadpoles have fundamentally the same
ultrastructure as those of vertebrates, indicating inheritance from a common an-
cestor. This was confirmed by Eakin (1965), who made a brief survey of the different
types of photoreceptors described in the literature and showed how different from
all others the tunicate tadpole or vertebrate type was. It is therefore not surprising
that M. i. miloni, which must be close to the common ancestor of tunicates and
vertebrates, had an optic system comparable both with that of a tunicate tadpole
and with that of an agnathan.
In summary, it seems that the brain and cranial nerves of M. i. miloni fundament-
ally resembled those of vertebrates in general, and primitive agnathans in particular,
and were also comparable with those of tunicate tadpoles. The trigeminal complex,
trigemino-profundus ganglia, optic, lateralis and olfactory systems were already
developed and the brain was divided into portions that are also recognizable in
both fish and tunicate tadpoles.
POSTURE, FEEDING AND MOVEMENT; It is fairly certain that M. i. miloni habitually
3io PRIMITIVE FOSSIL CHORDATES
lay with the big-plated side upwards. The reasons are: firstly, this side corresponds
morphologically to the upper side of cornutes (p. 289) ; secondly, it corresponds to
the dorsal side of fish; thirdly, the probably sensory peripheral canals, and the
eyes and peripheral grooves of M. mitra, were on this side ; fourthly, in this position
the more heavily armoured side would be upwards, which seems reasonable. The
ventral parts of the theca would certainly be partly buried in the bottom.
The posterior stem, is commonly bent ventrally in the fossils as found and would
have served as an anchor.
Feeding must have been microphagous, and the position of the mouth suggests
a deposit feeder. Water was probably pumped through the pharynx by muscles
internal to the flexible anterior ventral skeleton. This implies the existence of
a velar valve across the posterior margin of the buccal cavity. Pumping by the
ventral wall of the theca would not much disturb the mud beneath but would merely
raise and lower the dorsal surface.
The anterior stem is seldom well-preserved in M. i. miloni, but could probably
flex both vertically, by analogy with M. barrandei (p. 293), and horizontally, by
analogy with Mitrocystites mitra (p. 322). The roughly symmetrical, tadpole-like
shape of M. i. miloni suggests that the animal could swim forwards by lateral flexing
of the anterior stem. The extensive, soft tissue-filled spaces in the skeleton may
have assisted swimming by lightening the skeleton.
M. i. miloni could probably also crawl backwards pulled by the ventral flexing
of the stem. A backwards direction of crawling is suggested by the direction of
imbrication of anterior ventral plates (Fig. I3b ; PL 4, fig. 8) and the transverse
ridges (tr in Fig. I3b; PI. 4, fig. 8), steeper anteriorly than posteriorly, which cross
the posterior ventral part of the theca. Both these features would resist forward
movement. Also the ventral muscles of the posterior stem were probably larger
than the dorsal ones, suggesting that they delivered the power stroke.
The transverse ridges would be most useful when the animal, in crawling, pulled
the posterior stem from the sea bottom. This would tend to push the theca an-
teriorly and also exert a turning moment on it, so that the postero-ventral surface,
where the ridges are, would be driven hard into the mud. There are no yaw pre-
vention structures (anterior appendages or ventral spikes) on M. i. miloni, which
fact suggests that, in crawling, vertical flexing of the stem was more important
than horizontal flexing.
d. Mitrocystites mitra Barrande
SYSTEMATIC POSITION: Family Mitrocystitidae (as M itrocystella) . Genus Mitro-
cystites Barrande 1887, species Mitrocystites mitra Barrande 1887, the type species.
For an account of the systematics see Chauvel (1941).
OCCURRENCE : Sarka Beds (Llanvirn Series) and Dobrotiva Beds (Llandeilo Series)
of Bohemia. The most useful material, preserved in nodules, comes mainly from
the Sarka Beds of Sarka, near Prague, and Osek, near Rokycany. The associated
fauna indicates a shallow- water, marine environment.
WITH ECHINODERM AFFINITIES 311
MATERIAL: Narodni Museum, Prague (about 220 specimens); British Museum
(Natural History) (n specimens, E 7517, E 16057-9, E 16061-3, E 16068-9,
E 16089) ; University of Bonn (i specimen) ; Museum of Comparative Zoology,
Harvard (14 specimens Nos. 565 to 579); Royal Scottish Museum, Edinburgh
(i specimen) 1933.70.23; Sedgwick Museum, Cambridge (2 specimens) A48. 926-7.
GENERAL SHAPE AND PLATE NOMENCLATURE: The general shape of M. mitra is
very like that of M. i. miloni but broader. The sides of the theca are not so steep,
but slope smoothly into the posterior ventral skeleton.
IP
I mm
FIG. 23. Mitrocystites mitra Barrande. Reconstruction of external features, a. dorsal ;
b. ventral ; c. right ; d. anterior ; e. posterior aspects, bo = branchial opening ;
dn3 = depression associated with nerve n3 (optic depression) ; Ip = lateral pore ; mo =
mouth ; ng = narrow groove (lateral line) ; on3 = opening of nerve n3 (optic nerve) ;
or = oral plate ; pg = peripheral groove ; std = styloid ; tr = transverse ridge.
3I2
PRIMITIVE FOSSIL CHORDATES
^ __x MA mo
por-
mo
FIG. 230.
WITH ECHINODERM AFFINITIES
313
FIG. 23d.
The plates present in the theca are as follows :
Notation
M2L
M3L
M4L
M5L
M6L
MA
M2R
M4R
MSB
M6R
CIL
C2L
CA
VPL
VPM
Name
Left dorsal ist marginal
Left ventral ist marginal
Left 2nd marginal
Left 3rd marginal
Left 4th marginal
Left 5th marginal
Left 6th marginal
Anterior marginal
Right ist dorsal marginal
Right ist ventral marginal
Right 2nd marginal
Right 3rd marginal
Right 4th marginal
Right 5th marginal
Right 6th marginal
Left ist central
Left 2nd central
Anterior central
Right ist central
Right 2nd central
Left posterior ventral
Median posterior ventral
Right posterior ventral
ventral plates
Homologous plate in
M. i. miloni
MILD
M2L
?M3L
?M3L
M4L
M5L
MA
(M3L of miloni must corres-
pond to either M3L or M4L
of mitra, but it is not
possible to say which)
M2B
MSB
M5B
M6R
CL
CA
CR
ventral plates
THECAL OPENINGS : The mouth is very like that of M. i. miloni but the oral plates,
which number about fifteen, are shorter. The oral plates carry a hemicylindrical
groove on their inner, dorsal faces (hg in PI. 6, fig. 8) which may have housed a
sphincter muscle.
The mouth opens distinctly leftwards in the smallest specimen seen (maximum
thecal width 6-4 mm., PI. 8, fig. 5), and makes an angle of about 12° with a line
3H
FIG. 236.
joining the middle of the mouth to the middle of the cerebral depression. This
asymmetry is absent from the largest specimens (e.g. PI. 8, figs. I, 8) and so, by
extrapolation, was presumably even more marked during the earliest phases of
life history, before a skeleton was acquired. The mouth also faced leftwards in
adult M. i. miloni (p. 282, PI. 5, fig. 2, about 5°) and Chinianocarpos thorali (Ubaghs,
19610, fig. lA, B, and personal observation, about 35°) and this is presumably a
primitive characteristic of the Mitrocystitidae. It is interesting that the mouth
also faces leftwards in larval amphioxus (e.g. Willey 1894 : 143 ff.).
The branchial openings were situated near the posterior right and left corners
of the theca (bo in Fig. 23b, c and PI. 8, figs. 2-4). PL 7, figs. 2, 4 show the plates
associated with the gill opening on the left side of a single specimen. The break
in slope (bsl) in these figures is not explicable if the plates MILV, MILD and M2L
were merely sutured together, and indicates that the apposed faces of MILV and
MILD, posterior to the break in slope, were specialised to form articulation facets
(af) dorsal and ventral to an articulation. Movement about this articulation
would cause a gap to open between the left edge of MILV, anterior to the break in
slope, and M2L, above the gap. As in M . i. miloni, there was a median soft layer
in the ventral skeleton, continuations of which entered the dorsal skeleton posteriorly
and touched the inner faces of the dorsal skeleton laterally. The corresponding
parts of the inner faces are excavated to receive the soft layer (si in PI. 7, fig. 4).
It is apparent that the branchial openings would have been flanked by soft tissue
which, as in M. i. miloni and Cothurnocystis curvata, would have acted as a seal
when the opening closed.
The lateral line (ng in Fig. 23b, e, PL 8, fig. 3) is situated, as in M. i. miloni, on
On the dorsal surface are two pairs of openings not present in M . i. miloni. The
more anterior of these (on3 in Fig. 23a; PL 8, fig. i; PL i o, figs. 5,7, " paarige Gruben "
of Jaekel 1918 : 121) are the openings of the optic nerves (n3) on to the surface
(n3 are shown in PL 7, fig. 4; PL 8, fig. 10; PL 10, fig. 6). Each opening is often
preceded by a small, paired depression across the suture M2/3L and R, (dn3 in PL 8,
fig. i) which presumably carried a vesicle on the end of n3, i.e. an eye.
The more posterior pair of openings are termed lateral pores (Ip in Fig. 23a,
PL 8, fig. i; PL 10 figs. 4, 5, " Seitenporen " of Jaekel 1918 : 121). They straddle
WITH ECHINODERM AFFINITIES 315
the sutures MiLD/M2L and MiRD/M2R, and represent the openings on to the surface
of nerves n4 and n5 (Fig. 27a, b, see also PI. 6, fig. 6; PI. 7, fig. 4; PL 8, fig. 4 and
PL 10, fig. 6). The lateral pores are located at the deepest points of paired peri-
pheral grooves (pg) which, though not sharply delimited, are situated near the
: Buccal cavity Rectum
Pharynx
Atria
vX Primary anterior coelom ( f + f ^ Brain cavity and nerve canals
'MM: Posterior coelom Definite boundaries, visible dorsally
— Outline of theca Definite boundaries, invisible dorsally
Plate boundaries on dorsal external surface
FIG. 24. Mitrocystites mitra Barrande. Chambers of the theca, dorsal aspect.
og —oblique groove.
posterior, dorsal edges of the theca. The peripheral grooves are evidently homo-
logous with the peripheral canals of M. i. miloni which have the same position and
inner vation. The surface ornament of the plates is finer under the peripheral
grooves than elsewhere (PL 10, fig. 5), indicating that in life the grooves probably
contained soft tissue.
THE CHAMBERS OF THE THECA: The chambers of the theca differed very little
316 PRIMITIVE FOSSIL CHORDATES
from those of M. i. miloni but the intercameral ridges were less extensively calci-
fied, so that relationships are generally not so well shown.
The oblique groove is basically similar to that of M . i. miloni but its anterior
end is shallower (cf. PL 8, figs. 5, 10 with M. i. miloni in PL 5, figs. 7, 9). The
median branch is well developed (mb in PL 8, fig. 10; PL 10, fig. 6). The oblique
groove just posterior to it is not rounded in the way which, in M. i. miloni, suggests
contact with the oesophagus (p. 285), but this need indicate only a very small
difference in the position of the oesophagus. The separation (grp) between right
pharyngeal chamber and residual anterior coelom shows clearly in PL 10, fig. 6.
The part of the internal mould corresponding to the right pharyngeal chamber
FIG. 25. M. mitra. Reconstruction of the skeleton of a segment of the posterior stem.
a. anterior aspect ; b. left aspect ; c. ventral aspect of dorsal ossicle ; d. anterior aspect.
aig = anterior interossicular groove ; aiid = anterior, inner interossicular depression ;
aoid = anterior, outer interossicular depression ; cgap = canal leading to ganglionic pit ;
die = dorsal longitudinal canal ; epg = epidermal groove ; dvf = dorsoventral facet ;
gap = ganglionic pit ; iaf = interossicular articular facet ; Ig — lateral groove ; mg =
median groove ; mgne = neural part of median groove ; mgno = notochordal part of
median groove ; pig = posterior interossicular groove ; piid = posterior, outer, inter-
ossicular depression ; poid = posterior, outer, interossicular depression.
WITH ECHINODERM AFFINITIES 317
carries a series of weak corrugations (sp in PI. 10, fig. 6) which are absent from the
region corresponding to the anterior coelom. These corrugations are sometimes
seen in the pharyngeal regions of the internal mould of M. i. miloni in large speci-
mens (sp in PI. 10, fig. i), and can be compared with the striations on the walls
of the pharynx in Cothurnocystis elizae (p. 257, sp in Fig. 36, E; PI. 2, figs. 2, 5).
They may indicate folds in the wall of the pharynx, which would be appropriate
for a respiratory and food-collecting organ.
The posterior coelom is very much as in M . i. miloni. The rectum, however,
left it more anteriorly so that there is no rectal bridge. The rectal ridge is clearly
visible (rr in PI. 10, fig. 6). As in M. i. miloni the membrane limiting the posterior
coelom seems to have been continuous with that limiting the left pharyngeal
pi id
FIG. 25d.
chamber. The two chambers were separated only by a fold in this membrane on
the left side of the posterior coelom and this fold became less sharp anteriorly
(PI. 6, fig. 6; PI. 8, fig. 10).
The left atrium, perhaps because of the more anterior position of the rectum,
shows more clearly than in M. i. miloni (la in PI. 6, fig. 6; PI. 8, fig. 10; PI. 10, fig. 5).
The right atrium is very like that of M. i. miloni (ra in PI. 6, fig. 6).
The buccal cavity (be in PI. 8, fig. 10) was much as in M. i. miloni, but its wall
was less extensively calcified, so that it cannot be dissected out of the internal cast.
The olfactory openings (olo in PI. 8, figs. 5, 10; PI. 10, fig. 6) occupy exactly com-
parable positions.
THE STEM: This, again, much resembles that of M. i. miloni.
The posterior stem differs externally by having the dorsal ends of the ventral
plates everywhere internal to the dorsal ossicles. Paired dorso- ventral facets on
318 PRIMITIVE FOSSIL CHORDATES
the internal face of the dorsal ossicles (dvf in Fig. 25a, c; PL 9, fig. 5) are found
near the anterior, ventral corners of the ventral plates.
The soft parts are again reflected by the internal sculpture of the dorsal ossicles.
The ventral surface of any one of these is traversed by a median groove (Fig. 25a, c)
which is divided into an external, notochordal part (mgno) and a more median
neural part (mgne). From the neural part a pair of canals goes off in each segment
to ganglionic pits (gp). Anterior and posterior interossicular grooves are present
in the median plane (aig in PL 8, fig. 4). The dorsal longitudinal canal is stouter
idm
vm
vp
FIG. 26. M. mitra. Block diagram of posterior stem, dlv = dorsal longitudinal vessel ;
dnc = dorsal nerve cord ; do = dorsal ossicle ; idm = inner dorsal muscle ; iv =
interossicular vessel ; Ibv = lateral blood vessel ; Igc — lateral ganglion ; not =
notochord ; nv = notochordal vessel ; odm = outer dorsal muscle ; vm = ventral
muscle ; vp = ventral plate.
than in M. i. miloni. The interossicular articulations are situated as in M. i.
miloni. Anterior and posterior, inner and outer, interossicular depressions exist
(aiid, aoid in PL 6, fig. 9; aiid, aoid, piid, poid in Fig. 23a, c, d). The outer depres-
sions are shallower and wider than in M. i. miloni and the inner depressions
relatively much smaller.
A natural mould of the ventral surface of the dorsal ossicles (PL 9, fig. 5) gives
a representation of the soft parts. Here again a dorsal nerve cord (dnc) overlies
a notochord (not) and gives rise to paired, pear-shaped ganglia (ga). In some parts
of the specimen it can be seen that the ganglia were connected proximally to the
dorsal nerve cord and not to the notochord.
WITH ECHINODERM AFFINITIES 319
The notochord was laterally compressed, where the apposed interossicular grooves
came off but widened beneath the ganglia. Apposed interossicular grooves pre-
sumably carried an interossicular vessel going up through the dorsal nerve cord
to a vessel in the dorsal longitudinal canal. The lateral widenings of the notochord
may indicate lateral vessels coming off the notochord ventral to the skeleton. A
reconstruction of the soft parts of the posterior stem is shown in Fig. 26.
Medial and anterior stems differ little from those of M. i. miloni, but the anterior
stem had only six segments. On some specimens (PI. 8, fig. i; PI. 10, fig. 7) the
position of burial suggests that the anterior stem could flex from side to side.
THE BRAIN AND CRANIAL NERVES: The skeletal histology of M. mitra, which
affects the reconstruction of the cranial nerves, differs in some respects from that of
M. i. miloni. Thus: i. The median soft layer of the ventral skeleton (si in PI. 10,
fig. 8) was not dilated where nerves passed through it. 2. All plates of the ventral
skeleton, not only the more posterior ones, have an inner layer of calcite (il in
PL 10, fig. 4). It can therefore be shown that there was no soft layer of connective
tissue just within the outer calcite layer in the anterior ventral region. There is
no evidence concerning this point in M. i. miloni. 3. There were no irregular,
soft-tissue filled spaces in the dorsal skeleton. 4. As already mentioned (p. 315),
the intercameral ridges were less extensively calcified than in M. i. miloni. 5. The
outer surfaces of the central dorsal plates sometimes show near their centres
(PL 8, fig. i, fp.) a patch preserving the coarse fenestration of the juvenile skeleton
(cf. PL 8, fig. 5 and the developing calcite plates of crinoids shown by Seeliger 1892).
Three of these features make the reconstruction of the cranial nerves more difficult
than in M. i. miloni, namely the absence of dilatations in the ventral soft layer
and of spaces in the dorsal skeleton, and the less extensive calcification of the
intercameral ridges. Nonetheless, the two nervous systems were clearly very
similar and the detailed differences are of much interest.
The anterior part of the encephalic cast is much smaller than in M. i. miloni
(ap in Fig. 2ya-c; PL 8, fig. 9), and takes the form of a crinkling of the median
posterior dorsal suture (MIL/RD)- This crinkling is absent from all other sutures
and is therefore unlikely to represent a mere strengthening device.
The medial part of the encephalic cast is more clearly demarcated in dorsal
aspect from the posterior part of the cast than in M. i. miloni (Fig. 2ya; PL 6,
fig. 6; PL 8, fig. 10; PL 10, fig. 6; cf. PL 6, fig. i; PL 10, fig. 3 for M. i. miloni).
Its foramen (mpf in Fig. 2yb, PL 9, fig. 6) is much wider than in M. i. miloni (Fig.
igb ; PL 6, fig. 4) and grooves on the front of the hypocerebral processes (gmpn
in PL 8, fig. 6) indicate the proximal courses of the medial part (optic) nerves. It
therefore follows that the optic part of the brain and the bases of the optic nerves
were relatively bigger in M. mitra than in M . i. miloni. This recalls that, more
peripherally, the optic nerves (n3) were much bigger in M. mitra and continued on
to the dorsal surface of the theca, where each one ended in a vesicle or eye. In
M. i. miloni, on the other hand, the eyes, if they existed at all, were only vestigial
and the optic nerves, at least in the adult, did not connect with them. All parts
ascribed to the optic system were therefore better developed in M . mitra than in
M. i. miloni, which confirms that they had a common function.
320
PRIMITIVE FOSSIL CHORDATES
FIG. 27. M. mitra. Reconstruction of brain and cranial nerves, a. dorsal aspect;
b. anterior aspect of posterior part; c. left aspect for right part; ap = anterior part of
brain ; be = buccal cavity ; csb = carrot-shaped body (lateral line ganglion) ; csbn
= nerve to carrot-shaped body (nerve to lateral line ganglion) ; e = eye ; Imp =
lower medial part of brain ; mp = medial part of brain ; mpf = medial part foramen ;
mpn = median part nerves ; n0 = nerve leaving posterior coelom, near mid line ;
HI, z A, 2P, 3, 4, 5 = nerves of palmate complex; olo = olfactory opening ; pal = palmar
nerve ; pb = pyriform body ; pg = peripheral groove ; pp = posterior part of brain ;
ppn = posterior part nerve ; r — rectum ; ump = upper medial part of brain.
WITH ECHINODERM AFFINITIES
csbn
321
pg
'2 n
pal V "o imp
FIG. 2yb.
pal mp pp
ppn
Imp
FIG. 270.
The lower medial, or hypophyseal, part of the encephalic cast, as already mentioned,
is slightly swollen in M. mitra (PL 9, fig. 6) differentiating it from the optic part
of the encephalic cast.
The posterior part of the encephalic cast scarcely differs from that of M, i. miloni.
Turning to the palmate complexes, the palmar nerves (pal in Fig. 27a-c) did not
cause the front wall of the posterior coelom to calcify so extensively as in M. i.
miloni and consequently these nerves cannot be traced until they had already
begun to enter the ventral skeleton. Their courses at these points were nearly
vertical (pal in PL 10, fig. 8) as in M. i. miloni, and the left one presumably looped
over the rectum as in that form.
Of the branches arising from the palmar nerves, left and right nx, because of the
absence of dilatations in the ventral, soft layer, cannot be demonstrated in M.
mitra, though they doubtless existed. The nerves n2 are most proximally indicated
in one specimen (PL 10, fig. 8) just before the left one left MILV- They must have
GEOL. 1 6, 6. 3O
322 PRIMITIVE FOSSIL CHORDATES
run through VPL and R and left the ventral skeleton with the soft layer. They
can be traced again on the inner faces of M2L and R and then followed a course
indicated by left and right grooves in the skeleton, much as in M. i. miloni. Anteri-
orly the grooves turn abruptly downwards in the middle of MSL and R, and at these
points the nerves must normally have left the dorsal skeleton. In one specimen,
however, the left groove bends horizontal again and runs forward as far as the
anterior end of MSL (PI. 8, fig. 10). This suggests that left n2 divided into two
branches (n2A and n2p in Fig. 27a). n2p was thicker and innervated the anterior
part of the belly. n2A was thinner and probably innervated the mouth and lower
lip. The parts of the ventral skeleton innervated by these two branches can be
estimated by comparing PI. 8, fig. 8 and PL 8, fig. 10. There is no evidence as to
whether right n2 had comparable branches at its anterior end.
The nerves n3 of the palmate complex, or optic nerves, can in one case be traced
for a short distance in the ventral skeleton on the left side (PL 10, fig. 8). The canal
which here carried left n3 was compressed in section. The nerves n3 left the ventral
skeleton with the soft layer (PL 7, fig. 4) anterior to the branchial opening. They
then travelled upwards and forwards in paired grooves (PL 6, fig. 6; PL 7, fig. 4;
PL 8, fig. 10 and PL 10, fig. 6) which gradually deepened, leading finally to short
cylindrical canals (PL 7, fig. 4) that opened (ons) on the dorsal surface. The changes
in section of the nerves n3 — compressed in the ventral skeleton, becoming circular
peripherally — strongly confirm that the structures were indeed nerves.
The two pairs of nerves n4 and n5 must have had courses in the median layer
of the ventral skeleton very similar to those in M. i. miloni, though their exact
positions cannot be defined. The nerves entered MXL and RD with the median
soft layer, much as in M. i. miloni. Immediately afterwards the nerves n5 swung
outwards to join n4 (Fig. 27a, b; PL 8, fig. 10; PL 10, fig. 6) and n4 and n5 then on
both sides ran upwards together, into the lateral pores, to innervate the peripheral
grooves.
The pyriform bodies and lateral-line ganglia are much as in M. i. miloni except
that the pyriform bodies were more symmetrical. The dorsal and ventral cupules
enclosing the left pyriform body show in PL 8, figs. 2, 4. The lateral-line ganglion
(csb) is shown in PL 10, fig. 8.
The olfactory nerves must have consisted, as in M. i. miloni, of isolated fibres
in the dorsal skeleton connecting the olfactory openings (olo) in the buccal cavity
with the telencephalon (ap).
The nerves n0, in the absence of dilatations of the ventral soft layer, cannot be
demonstrated in M. mitra but no doubt existed.
In summary, therefore, some features of the cranial nerves show more clearly
in Mitrocystites mitra than in M. i. miloni. These features relate mainly to the
optic system, the anterior end of the left maxillary trigeminal (n3) and the hypo-
physeal part of the brain (Imp). Some details of the dorsal sensory complex (i.e.
peripheral grooves and n4 and n5) also differ.
POSTURE, FEEDING AND MOVEMENT: M. mitra must have resembled M. i. miloni
in posture, feeding and movement. Some specimens (PL 8, fig. i; PL 10, fig. 7)
show more clearly than in M. i. miloni that the proximal stem could bend from side
WITH ECHINODERM AFFINITIES 323
to side. The theca probably lay more deeply buried in the mud than that of M. i.
miloni since there is no sharp " change in slope " between marginal plates and
posterior ventral skeleton, and the transverse ridges are restricted to the higher
parts of the theca. The theca of M. mitra can be compared with the shell of the
Recent bivalve Pecten maximus, which habitually lies with the convex valve down-
wards, and with the flat valve about level with the sea-floor.
IV. DISCUSSION
a. Cornutes and Mitrates
The imperfection of the fossil record makes it impossible to reconstruct the
phylogeny of cornutes and mitrates in detail. Only one species of cornutes is
known from the Middle Cambrian, whilst none is known from the Upper Cambrian.
Five specimens (placed in two species and genera) are known from the Lower
Tremadoc Series (Ubaghs 1963). In the Upper Tremadoc the cornute record is
better but incomplete, since only one specimen is known from outside Europe
(Gigout 1954). The only later cornutes described in the literature are those from
the Ashgill Series of Scotland.
The record of the earliest mitrates is little better. The two earliest families,
the Lagynocystidae and Mitrocystitidae, are both first known from the Upper
Tremadoc or Lower Arenig Series. The species which represent those families
at this horizon (Peltocystis cornuta Thoral and Chinianocarpos thorali Ubaghs)
resemble each other enough to suggest a common origin from the cornutes. They
also differ enough to indicate a long, unrecorded period of divergence. In later
rocks the mitrates are fairly common, though they have not received much attention.
Nonetheless certain deductions concerning the phylogeny of cornutes and early
mitrates are possible, despite this lack of fossils. Firstly, the cornutes and mitrates
are certainly closely related to each other, and the establishment of a group to
contain both (Class Stylophora, Subphylum Calcichordata) is justified. Secondly,
the mitrates certainly arose from the cornutes, rather than the converse. Thirdly,
the line of descent from the earliest known cornute (Ceratocystis) to Mitrocystites
and Mitrocystella can be postulated from known forms. This reconstructed line
of descent is essentially a working hypothesis, and although not entirely consistent
with the stratigraphical order of first known occurrences, one must keep in mind the
patchy fossil record. The Lagynocystidae are not further considered here, and
until they have been studied in detail it is pointless to fit them into a general scheme.
The close relationship of cornutes and mitrates is indicated by a number of
features in common: i. Both groups had a mouth near the front end of the theca.
2. In both groups the skeleton was made of plates, each a single calcite crystal.
3. Both groups had a flattened theca, adapted for lying on the sea-floor, with dorsal
and ventral surfaces. 4. Both groups had marginal plates, usually numbering
twelve to fifteen, round the theca. Thus, counting dorsal and ventral first marginals,
but excluding appendages, C. elizae had thirteen marginals, C. curvata had twelve,
Chinianocarpos thorali had twelve, M. i. miloni had fourteen and M. mitra fifteen.
GEOL. l6, 6. 3°§
324 PRIMITIVE FOSSIL CHORDATES
5. Both groups had a basically similar arrangement of thecal chambers. 6. Both
groups had a brain and paired pyriform bodies at the anterior end of the stem.
7. In both groups the stem ended abruptly. 8. In both groups an anterior, tetra-
serial part of the stem was adapted for flexing sideways and a posterior part for
flexing vertically. 9. Within the stem, both groups certainly had segmented muscle
blocks and a chambered organ or notochord and both almost certainly had a ped-
uncular nerve (dorsal nerve cord). 10. Both groups were pharyngotrematous.
Cornutes had external branchial slits; Mitrates had presumed internal branchial
slits and branchial openings, n. Most cornutes had the anus, either internal or
external, hust left of the stem while mitrates had the anus internal and just left
of the stem. Against this, however, the earliest known cornute (Ceratocystis perneri)
had the anus right of the stem (personal observation).
That mitrates were descended from cornutes, rather than the converse, is indi-
cated by the fact that: i. The earliest known cornute is Middle Cambrian in age,
while the earliest known mitrates are Upper Tremadoc or Lower Arenig Series.
2. The mitrates give the impression of imperfect bilateral symmetry, imposed on
a basic, cornute-like asymmetry. 3. One of the earliest known mitrates (Chiniano-
carpos thorali) has many cornute-like features, i.e. big plates just ventral to the
mouth, a partly flexible thecal roof, an oblique groove borne entirely on marginal
plates, not very massive dorsal stem ossicles, the ability to flex the posterior stem
upwards, and a very short lateral line. The mitrates probably arose from the
cornutes during the Upper Cambrian.
The line of descent from Ceratocystis to Mitrocystites and Mitrocystella can be
reconstructed as follows :
1. Ceratocystis. Theca boot-shaped, rigid. Anterior appendages present. Anus
external, right of the stem. Gill slits external, left of the stem. No lateral line.
Only known occurrence, Middle Cambrian (Ceratocystis perneri Jaekel).
2. Cothurnocystis (americana type). Theca boot-shaped. Floor of theca rigid.
Roof of theca a flexible integument. Anterior appendages not known. Anus
not known. Gill slits external, left of stem. No lateral line. Only-known occur-
rence, Lower Tremadoc Series.
3. Cothurnocystis (elizae type). Theca boot-shaped. Floor of theca an integu-
ment crossed by a strut. Roof of theca a flexible integument. Anterior appendages
present. Anus external, left of the stem. Gill slits external, left of stem. No
lateral line. First known occurrence, Upper Tremadoc or Lower Arenig Series
(C. primaeva Thoral).
4. Phyllocystis. Theca leaf-shaped. Floor of theca an integument crossed by
a thin, curved and probably functionless strut. Roof of theca a flexible integument.
Anterior appendages absent. Anus external, left of the stem. Gill slits external,
left of the stem. No lateral line. First known occurrence Lower Tremadoc Series
(Phyllocystis sp., Ubaghs 1963).
5. Chinianocarpos. Theca leaf-shaped. Floor of theca an integument with no
strut. Roof of theca mainly rigid, with a small area of integument. Anterior
appendages absent. Anus internal, left of stem. Gill slits internal, paired. Lateral
line a small pit. Only known occurrence Upper Tremadoc or Lower Arenig Series
(C. thorali Ubaghs 19610;) .
WITH ECHINODERM AFFINITIES 325
6. Mitrocystites & Mitrocystella. Theca leaf-shaped. Floor of the theca an
integument with no strut. Roof of theca entirely rigid. Anterior appendages
absent. Anus internal, left of stem. Gill slits internal, paired. Lateral line a
groove. First known occurrence Llanvirn Series (Mitrocystites mitra Barrande and
Mitrocystella barrandei Jaekel).
The line of descent represented by Cothurnocystis curvata probably arose from
a C. elizae-like ancestor. In most respects C. curvata differs more from Ceratocystis
perneri than does C. elizae. Thus, unlike both C. perneri and C. elizae, C. curvata:
i. Has no right oral appendage. 2. The anus is internal. 3. The mouth is dorsal,
instead of anterior. 4. The anterior margin is strongly convex upwards. 5. The
stylocone tapers very abruptly. In addition, the branchial skeleton of Ceratocystis
perneri needs little modification to produce that of C. elizae. It needs much modi-
fication, on the other hand, to produce that of C. curvata. The earliest-known
representative of the C. curvata group, like that of the C. elizae group, is Upper
Tremadoc or Lower Arenig in age (Ubaghs, personal communication). The internal
anus may be a genuine point of comparison with mitrates, or may have been acquired
independently.
The changes involved in going from Cothurnocystis of elizae type, through Phyllo-
cystis and Chinianocarpos to Mitrocystites or Mitrocystella are worth stating in
detail, since this course of evolution includes the origin of mitrates from cornutes.
1. Mouth
i. A big plate (MA) developed dorsal to the mouth, as in C. thorali.
ii. Subsequently the big plates forming the ventral mouth frame (MSR, MGL of
C. elizae, MSR, IVLn, of C. thorali) became reduced, so that they no longer met at
the mid-ventral line. At about the same time MA fused to these same plates,
iii. Presumably later than (i), the oral plates of the upper lip were lost.
2. Thecal shape and skeleton of theca
iv. Appendages and anterior ventral spikes were lost, as in Phyllocystis.
v. At about the same time the theca became more symmetrical, as in Phyllocystis.
vi. Somewhat later than (iv) and (v) the posterior, ventral spikes were lost. They
are present but weak in Phyllocystis.
vii. The strut, which had functioned to prevent collapse of a concave anterior
margin when the muscles of the integuments contracted, was lost. When this
margin became convex, the strut lost its function. In Phyllocystis it is, accordingly,
very slender and curved. It is absent in Chinianocarpos thorali where, as com-
pared with Phyllocystis, the roof of the theca is more rigid and the floor is not in
one plane.
viii. The marginal plates grew forward from the posterior, right-hand part of
the theca, carrying the oblique groove with them, as in C. thorali.
3. Thecal chambers and gill slits
ix. The right pharyngeal chamber pouched out from the left one, and right gill
slits appeared. In addition the right atrium and gill opening appeared, if the gill
slits were already internal.
326 PRIMITIVE FOSSIL CHORDATES
x. The pharyngo- visceral line (oblique groove) and anterior coelom came to be
fixed to the ceiling of the theca. This could have been either the precondition for,
or the result of, the appearance of the right pharyngeal chamber (ix). It was
connected with the expansion of the right, posterior, marginal plates (viii).
xi. The atria appeared. Right and left atria probably arose simultaneously if
the right gill slits had appeared already (ix). Otherwise the left atrium preceded
the right one.
4. Stem
xii. The posterior stem developed the ability to flex downward as well as upward.
xiii. In connection with this, the ventral posterior stem ossicles became less
massive and were finally reduced to paired ventral plates, and the stylocone disap-
peared. Conversely, paired dorsal plates fused, giving rise to massive ossicles.
Interossicular articulations appeared, and then, later, the styloid arose by fusion
of the two most anterior of these ossicles.
xiv. Subsequently the posterior stem lost the ability to flex upwards.
5. The brain and cranial nerves
xv. The first dorsal marginals enlarged and grew backwards, so enveloping the
front of the brain and the dorsal sides of the pyriform bodies.
xvi. At about the same time the first ventral marginals became separated from
the brain, though they retained contact with the pyriform bodies.
xvii. The optic nerves pushed upward and opened on to the dorsal surface.
xviii. The lateral line and its nerve supply appeared.
xix. The palmate complexes either arose or, as seems more likely, became enclosed
in skeleton.
xx. The olfactory system either arose or became enclosed in skeleton.
Changes in the stem and theca can be explained by changes in the manner of
movement. When an animal like C. elizae crawled backwards by sideways flexing
of the anterior stem, the anterior rigid appendages and the ventral spikes prevented
yaw and resisted forward slipping (p. 265). Such a form as Phyllocystis , with
weak, posterior ventral spikes, a symmetrical theca and no anterior appendages
or anterior ventral spikes, probably crawled backwards by flexing the anterior
stem downwards, so pushing the rather stiff posterior stem anteriorly and ventrally
into the mud. Yaw prevention devices would not be needed and were lacking.
The weak posterior ventral spikes would function during the return stroke of the
stem, which would exert a turning moment on the theca. This moment would
push the posterior theca, where the spikes were, into the mud and prevent the
theca from slipping forwards.
The mitrate ability to flex the posterior stem ventrally, with all its related changes,
developed because this helped the anterior stem in the work of pulling the theca
backwards. The transverse ridges on the postero-ventral surface of the theca of
mitrates served the same function as the posterior ventral spikes of Phyllocystis.
WITH ECHINODERM AFFINITIES 327
In conclusion, the broad way in which cornutes and mitrates are related is fairly
clear. Large morphological gaps remain to be filled, however, partly by new
collecting, and partly by re-examining old material.
b. Stylophora, echinoderms, hemichordates and chordates
The relations of Stylophora with other groups, and the proposal to transfer them
from the Echinodermata to the Chordata as Subphylum Calcichordata, will now
be discussed. This reallocation is less radical than at first appears, since zoologists
agree that echinoderms and chordates are related. The Hemichordata are here
regarded as a phylum separate from, though related to, the Chordata, following
Barrington (1965) and Hyman (1959).
The zoological argument relating echinoderms and chordates has three aspects.
The first links echinoderms and hemichordates, the second links hemichordates
and chordates, and the third links echinoderms and chordates directly.
The aspect of the argument linking echinoderms and hemichordates can be
stated as follows :
i. Both groups have radial cleavage. 2. Both sometimes have similar larvae.
3. In both, the blastopore becomes the larval anus. 4. Both are tricoelomatous.
5. In both, the protocoele develops an opening to the exterior on the left side of
the larva. 6. In both, a pulsatile vesicle (heart of hemichordates, madreporic
vesicle of echinoderms) arises in close association with the protocoele (Narasim-
hamurti 1931 : 484, and earlier authors). The argument relating hemichordates
and echinoderms is well summarised by Hyman (1959 : 197). A most elaborate
series of echinoderm, hemichordate homologies was proposed by Gemmill (1914 :
277).
The aspect of the argument linking hemichordates and chordates depends mainly
on the presence of gill slits in both groups (Hyman 1959 : 201). In addition, both
can have a collagen-rich mesodermal skeleton, are deuterostomatous and have
radial cleavage.
The third aspect of the argument, which links echinoderms and chordates directly,
depends on the presence in both groups of radial cleavage, a mesodermal skeleton
and deuterostomy, and the possible broad homology of water vascular and hypo-
physeal systems (Goodrich 1917).
The relationship between Stylophora and echinoderms, though less close than
that with the chordates, is not in doubt. Stylophora, like all echinoderms, have
a skeleton in which each plate is a single crystal of calcite. In addition, anterior
and posterior coeloms of Stylophora may correspond to left and right somatocoels
in echinoderms. Further, the Stylophora have a particular relationship with
stalked echinoderms (Crinozoa, Matsumoto 1929) since: I. In both groups there is
a stem. 2. Both groups have a chambered organ and peduncular nerve in the
stem, an aboral nerve centre oral (anterior) to it and nerves radiating from the
aboral nerve centre to the theca. 3. Both groups have the mouth at the end of
the theca farthest from the stem. 4. Among Crinozoa, crinoids at least are typically
attached by the distal end of the stem. The abrupt end of the stem of Stylophora
328 PRIMITIVE FOSSIL CHORDATES
strongly suggests fracture and may indicate that a larval stylophoran attached
by a hold-fast at the end of the stem, from which it subsequently broke away.
5. The vestibule of crinoids may correspond to the buccal cavity of Stylophora.
6. The broad lumen of the anterior stem of Stylophora compares with a similar
broad proximal lumen in solute " carpoids ", many primitive crinoids, and many
eocrinoids and rhombiferan cystoids. The Stylophora differed from echinoderms
most importantly by having branchial slits and no obvious water vascular
system.
Crinozoa may possibly have arisen from Stylophora by the loss of branchial slits,
rather than the converse. The same line of speculation suggests that Stylophora
may have derived directly from Hemichordata.
Turning now to the chordate affinities of the Stylophora, of the forms here studied
the Mitrocystitidae, in particular, in many ways resemble tunicate tadpoles. Thus :
i. Both are clearly divided into a body (theca) and a postanal tail (stem). 2. Both
have a dorsal nerve cord resting directly on a notochord, the latter confined to the
stem or tail. 3. Mitrocystitidae and appendicularian tadpoles (Martini 1909) have
paired segmental ganglia in the stem or tail. 4. The brain of Mitrocystitidae had
hypophyseal, optic and medullary parts which can also be recognised in tunicate
tadpoles. 5. Both Mitrocystitidae and tunicate tadpoles have paired atria. 6.
Both Mitrocystitidae and tunicate tadpoles have the rectum opening into the left
atrium.
It should be emphasized that tunicate tadpoles resemble mitrates rather than
cornutes in the paired atria and gill slits, the rectum opening into the left atrium
and the subdivisions of the brain. A mitrocystitid, in fact, could be briefly de-
scribed as a giant, calcite-plated tunicate tadpole. Pending further study, it is
uncertain how far this description would also apply to a lagynocystid mitrate.
If, as argued below, the extant chordate subphyla have risen only once from the
Stylophora, then there are arguments which suggest that the Mitrocystitidae rather
than Lagynocystidae were their point of origin.
Mitrocystitidae most differed from tunicate tadpoles, apart from size, in the
abruptly ending stem with its posterior portion adapted to vertical flexion, the
calcite skeleton and the blood system of the stem. Further, larval Mitrocystitidae,
like Stylophorans in general, may have been anchored for a time by the posterior
end of the stem. Tunicate larvae, on the other hand, attach by adhesive papillae,
at the anterior end of the body, which may possibly be homologous with the cement
glands of many fish and amphibians.
Relationship between Cephalochordata and Mitrocystitidae is indicated by the
following points: I. Both groups have a dorsal nerve cord and notochord, and
segmentally repeated muscle blocks in a postanal tail. 2. Both groups have internal
gill slits, with, probably in both, the left ones appearing before the right ones in
ontogeny. 3. The left-facing mouth of larval amphioxus can be compared with
that of mitrocystitids. Relationships of cephalochordates with mitrates more
than with cornutes is suggested by the paired, internal gill slits, with the left ones
appearing first in ontogeny. Relationship with primitive mitrocystitids rather
than lagynocystids or advanced mitrocystitids is particularly indicated by the
WITH ECHINODERM AFFINITIES 329
left-facing mouth, for, of all known Stylophora, Chinianocarpos thorali has the
most left-facing mouth, while lagynocystids have the mouth facing right.
Cephalochordates differ most obviously from mitrates in that: I. They lack a
calcite skeleton. 2. The tail is entirely adapted for lateral flexion and does not
end abruptly. 3. The longitudinal caudal blood vessels are ventral to the noto-
chord. 4. Myotomes, notochord and dorsal nerve cord extend to the front end
of the animal. 5. Segmental (dorsal root) ganglia are lacking and ventral spinal
roots exist. 6. There is no brain. 7. The anus, though facing left, is external.
8. Anterior, larval adhesive organs, which were presumably lacking in mitrates if
the larvae attached by the stem, have been reported in Amphioxus (van Wijhe
1925)-
Mitrocystitidae resemble Agnatha in the following ways: i. In both groups the
dorsal nerve cord is dorsal to, and rests on, the notochord and gives rise to paired
segmental ganglia (dorsal root ganglia of agnathans). 2. Both groups have seg-
mented muscle blocks in the postanal stem or tail. 3. In both groups the brain lies
at the anterior end of the notochord and can be divided into medullary, optic,
hypophyseal and olfactory portions. 4. In both groups the cranial nerves include
olfactory, lateralis, optic and trigeminal complexes. In both the trigeminal complex
has trigemino-profundus ganglia and probably mandibular and maxillary branches.
5. Both groups have paired gill slits.
Paired gill slits and the subdivisions of the brain and the cranial nerves connect
the agnathans with the mitrates rather than the cornutes, and the existence of the
lateralis complex connects Agnatha with Mitrocystitidae rather than Lagynocys-
tidae.
Among agnathans, the earliest and most primitive Heterostraci (Cyathaspididae)
are particularly linked with Mitrocystitidae by having paired gill openings, small
eyes, paired olfactory nerves opening into the roof of the buccal cavity, no pineal
eye, and primitively marine habitat (Denison 1956, 1964; White 1958).
The most important differences between Mitrata, in particular Mitrocystitidae,
and Agnatha are: i. Agnathans, like vertebrates and other extant chordates, have
a uniform tail, not ending abruptly, with the longitudinal caudal vessels ventral
to the notochord. 2. If agnathans have a hard skeleton it is formed mainly of
hydroxyapatite, not calcite. This is true of vertebrates in general, whose only
purely calcitic parts are the otoconiae of the acustico-lateralis system. 3. The
spinal nerves of agnathans have separate dorsal and ventral roots. 4. The anus of
agnathans is median and external. 5. The brain of agnathans is longer and extends
farther forward. 6. Agnathan eyes are often better developed. 7. The acustico-
lateralis system of Agnatha includes ears.
Two features that the earliest agnathans may have lacked, although they occur
in most vertebrates, were a closed circulatory system and oculo-motor muscles,
for both these features are absent in myxinoids.
As regards larval attachment, recently hatched anuran tadpoles and the young
larvae of many archaic living fish such as dipnoans, Polypterus, Amia, Lepisosteus
and Acipenser attach themselves by cement organs near the anterior end of the
body (Kerr 1919, esp. p. 178 ff.). These organs are likely to be homologous in all
330 PRIMITIVE FOSSIL CHORDATES
the cases cited and, as already mentioned, they may possibly be homologous with
the adhesive papillae of tunicate tadpoles. They may also be homologous with
the adhesive papillae reported in amphioxus.
The evidence for a relationship between Stylophora and the extant chordate
subphyla can therefore be summarised by saying that all Stylophora had branchial
slits, a stem (or tail) which is post-anal and contains segmental muscle blocks, a
notochord with a brain at the front of it, and a mouth at the front end of the body.
Furthermore the Mitrocystitidae, at least, resembled extant chordates in having
paired branchial slits, dorsal nerve cord and segmental ganglia. The Mitrocysti-
tidae, in particular, had a number of additional resemblances to each of the three
extant subphyla, related especially to the cranial nerves and brain and to asym-
metries of structure. These resemblances are most unlikely to be coincidental
and clearly indicate that the extant subphyla of chordates were descended from
Stylophora. It therefore seems just to transfer the Stylophora from the Echino-
dermata, which they resemble less markedly, to the Chordata. Since the Stylo-
phora have resemblances to all the extant subphyla of chordates, but cannot clearly
be placed in one rather than another, and since they also have features that distin-
guish them as a group from all the extant subphyla, it is reasonable to establish
a new subphylum — the Calcichordata — to receive them.
The differences which separate all Stylophora from all extant chordates are the
calcite skeleton, the adaptation of the posterior part of the stem for vertical flexion,
the abrupt end of the stem which may imply attachment by the stem in the larva,
and the probable presence of a longitudinal blood vessel within the notochord.
These differences suggest that the other chordates have arisen from Stylophora
only once. If this is the case it is the mitrates, and among mitrates the Mitrocys-
titidae rather than the Lagynocystidae, which were the group from which these
other chordates arose, since Lagynocystidae lack the lateralis system (unlike Agnatha
and fish) and have the mouth facing somewhat to the right (unlike larval amphioxus).
Further, it is probably very primitive mitrocystitids which are in question since
the earliest-known agnathans, which are also the earliest-known chordates other
than calcichordates, are Lower Arenig in age (Bystrov 1955 : 473), while the earliest-
known mitrocystitid (Chinianocarpos thorali) is Upper Tremadoc or Lower Arenig.
This is supported by the fact that C. thorali, more than later mitrocystitids, has a
mouth opening strongly to the left.
It should be mentioned that some peculiarities of the peduncular blood system
of the Mitrocystitidae particularly studied here, i.e. the dorsal longitudinal blood
vessel with interossicular vessels going up to it through the dorsal nerve canal,
may have been absent from the earliest Mitrocystitidae since no dorsal longitudinal
vessel exists in the Lagynocystidae. Alternatively the dorsal vascular complex
may have been lost in subsequent evolution.
It is fairly certain that the Stylophoran calcite skeleton could not have directly
given rise to an apatite skeleton because: I. Calcite cannot gradually be converted
to apatite, since there is nowhere in the the calcite lattice for the insertion of phos-
phorus ions. 2. The earliest agnathans were probably either naked or covered with
loose denticles or scales, for the Arenig forms are known only as dermal denticles
WITH ECHINODERM AFFINITIES 331
(Bystrov 1955) or perhaps as fragments of scales (0rvig 1958 : 4). Middle Ordo-
vician agnathans, also, had skeletons consisting basically of small scales or plates,
sometimes fused over the head region. Big plates superficially resembling those
of Mitrocystitidae only developed later (Tarlo 1962; Denison 1964). In addition
both Cephalaspidae (Westoll 1945 : 345) and primitive Osteostraci (White 1958;
Denison 1964 : 459) had long, unossified larval stages. 3. Vertebrate apatite is
seeded extracellularly by collagen fibrils with 650 A repetition (e.g. Glimcher in
Sognnaes 1960). Echinoderm calcite, and therefore presumably calcichordate
calcite as well, is seeded from a tiny calcite crystal in a vacuole, intracellularly
(Bevelander & Nakahara in Sognnaes 1960). These two processes are totally
unlike.
Skeletal calcite was therefore most probably lost in the course of evolution, pro-
ducing a cartilaginous skeleton resembling that which occurs in some holothurians.
An apatite skeleton arose later, by seeding of apatite round the collagen fibrils. This
may have happened more than once. It is interesting that the ground-mass of
echinoderm calcite, like cartilage, contains abundant collagen fibrils (Randall et
al. 1952).
The history of the evolution of other chordates from calcichordates may therefore
have been somewhat as follows. In the Upper Cambrian, or at latest Tremadoc
Series, a population of primitive mitrates which lived in the shallow sea and were
most probably mitrocystitids resembling Chinianocarpos, took to swimming more
and more continuously in a forward direction, like tadpoles, by flexing the anterior
part of the stem from side to side.
A member of the population that did this had the rudiments of a lateral-line
system, optic, olfactory and trigeminal cranial nerves, a tunicate-vertebrate ultra-
structure in its visual cells, and a basically fish-like brain. It also had paired
atria, paired gill openings and paired gill slits, with the left gill slits preceding the
right ones in ontogeny. The rectum opened into the left atrium. The stem had
an abrupt posterior end, indicating that the larva had, for a short time, been attached
by the end of the stem. The stem was divided into an anterior, laterally flexing
part and a posterior, vertically flexing part. In the stem were segmented muscle
blocks, a notochord which ended at the front end of the stem where the brain was
sited, a dorsal nerve cord, and paired ganglia located between muscle blocks. A
blood vessel probably ran down the middle of the notochord. Because of its un-
symmetrical front end, the animal probably rotated round its longitudinal axis
as it swam, in which respect it may have differed from later mitrocystitids.
As an adaptation to swimming the skeleton grew lighter by the appearance of
connective-tissue-filled spaces. These finally coalesced and calcite disappeared
except, perhaps, for particles in the lateralis system (otoconiae), without which,
in the absence of any skeleton heavier than water, the lateralis system would
scarcely have functioned (Pumphrey 1950 : 12). Any remaining skeletal tissue
was soft and collagen-rich and resembled cartilage.
At the same time the anterior part of the stem expanded at the expense of the
posterior part, which was less and less used for anchorage and creeping. Finally
these functions disappeared, and even larval attachment by the end of the stem
332 PRIMITIVE FOSSIL CHORDATES
was given up. The previous larval hold-fast therefore remained attached to the
stem in the adult, instead of breaking away from it. There thus arose an organ
closely resembling a normal, chordate tail.
As further adaptation to swimming, the sense organs and nervous system increased
in complexity. The eyes moved forwards, so as to be better placed to see what
the animal was swimming towards, and the brain grew longer. The lateral line
system spread as a network over the whole body.
The next stage began when these soft-bodied animals again became temporarily
attached as juveniles, probably while still in the yolk-feeding stage. Attachment
this time took place by cement organs or adhesive papillae near the front end of
the body.
One group of such animals gradually extended this period of attachment until,
finally, their adults became completely non-motile, lost most of their sense organs,
their tails and their brains, developed a coat of tunicin and became urochordates.
The tadpole-like larvae of this group also became simplified to some extent, particu-
larly as regards the nervous system, but retained most of the features of the ancestral
juvenile stage which much resembled the ancestral adult. One ancestral feature
retained by the tadpoles was rotation during swimming.
In other descendants of the animals which had adopted anterior, larval attach-
ment, the period of attachment remained very temporary. Since the adults remained
able to swim, further modification of the tail took place, i.e. the ventral spinal
roots separated from the dorsal roots and the longitudinal blood vessel migrated
ventrally out of the notochord, if this had not happened already. In addition,
the anus became external though it still opened leftward.
From the animals so modified, evolution proceeded in two directions. In one
population, perhaps as an adaptation to burrowing, the tail somites, notochord
and dorsal nerve cord extended forward to the anterior end of the body with the muscle
blocks outside the atria. The atria therefore united, and came to open ventrally.
This population lost most of its sense organs, including the optic, olfactory and
lateralis systems, and the dorsal root ganglia disappeared. In addition, the forward
growth of the myotomes eliminated the brain as a rather unfortunate embryological
consequence (Newth 1951 : 256). This population also developed nephridia-like
excretory organs, unlike those of any other chordates. It retained the leftward-
facing larval mouth, the left gill slits that preceded the right gill slits in ontogeny,
and the tendency to rotate during swimming of the calcichordate ancestor. Thus
arose the Cephalochordata.
From the population that produced the cephalochordates, another group of
animals arose. In these, again, the attached phase of the larvae remained temporary,
but the adults remained habitual swimmers in water rather than becoming burrowers.
They ceased to rotate as they swam, however, which allowed the sense organs to
increase greatly in complexity and accuracy. True eyes with lenses were probably
evolved at this stage, and parts of the lateralis system sank into the body to function
as accelerometers or ears. The bodies of these animals became more symmetrical.
The anus became median. Right and left gill slits came to appear at the same time
in ontogeny. Kidneys developed. Also, and perhaps more than once, apatite,
WITH ECHINODERM AFFINITIES 333
seeded by collagen fibrils, produced a hard skeleton. These animals were the
vertebrates. In their basic features they already existed in Arenig times.
The foregoing story is admittedly speculative, but differs from previous specu-
lations on the origin of vertebrates in that it starts from a known beginning.
V. CONCLUSIONS
a. Phyletic and systematic position
A study of two members of the Order Cornuta Jaekel 1900, Cothurnocystis elizae
Bather, and Corthurnocystis curvata Bather, and two members of the Order Mitrata
Jaekel 1918, Mitrocystella incipiens (Barrande) miloni Chauvel and Mitrocystites
mitra Barrande, reveals a basically similar anatomy in all. This justifies the placing
of Cornuta and Mitrata in a larger group, the Stylophora Gill & Caster 1960, here
regarded as a class. It is fairly certain that the Mitrata evolved from the Cornuta,
rather than the converse.
The Class Stylophora is more closely allied to extant chordate subphyla than to
any echinoderms, and is better placed in the Phylum Chordata than in the Phylum
Echinodermata. Since it cannot be allocated to any of the extant chordate sub-
phyla, and has features which distinguish it from these subphyla collectively, it
is necessary to establish a Subphylum Calcichordata (Jefferies 1967) to receive
the Class Stylophora.
With Gislen (1930), the Calcichordata are here regarded as ancestral to the other
subphyla of Chordata. An Upper Cambrian mitrocystitid probably evolved into
a soft-bodied, free-swimming form which gave up larval attachment by the end
of the stem. This free-swimming form later took to larval attachment by cement
organs near the front of the body, and by various modifications gave rise first to
the Urochordata and then in turn to the Cephalochordata and Craniata.
b. Thecal openings
A large mouth at the anterior end of the theca is present in all four forms studied.
In adult Mitrocystella incipiens miloni and, to a greater extent, in juvenile Mitro-
cystites mitra, the mouth opened distinctly leftward. This asymmetry was even
more strongly marked in the earliest-known mitrocystitid, Chinianocarpos thorali.
It can be compared with the leftward-facing mouth of larval amphioxus.
External branchial slits, which had the mechanical structure of outlet valves,
were present in Cothurnocystis curvata and Cothurnocystis elizae on the left, dorsal
part of the theca. Internal gill slits were presumably present on both sides in
Mitrocystites mitra and Mitrocystella incipiens miloni. They were separated from
paired branchial openings by atria.
The anus in Cothurnocystis elizae was external and just left of the stem. The
anus of C. curvata was also just left of the stem but was internal, opening into the
most median gill slits. In Mitrocystella incipiens miloni and Mitrocystites mitra
the anus was likewise internal, opening into the left atrium as in a living tunicate
tadpole.
334 PRIMITIVE FOSSIL CHORDATES
The lateral line was developed just to the right of the stem in M. mitra and
M. i. miloni.
Other thecal openings in M. mitra were the openings bringing the optic nerves
(n3) on to the dorsal surface and the lateral pores bringing nerves n4 and n5 on to
the dorsal surface.
In M. i. miloni the optic nerves n3 were vestigial, and nerves n4 and n5 did not
open on the dorsal surface.
c. Thecal chambers
The theca of C. elizae was divided into buccal cavity, pharynx and anterior and
posterior coeloms. These probably also all existed in C. curvata, though the separate
existence of pharynx and anterior coelom cannot be demonstrated directly in that
species.
The theca of M. i. miloni and M. mitra was divided into buccal cavity, left pharyn-
geal chamber, that corresponds to the pharynx of cornutes, right pharyngeal chamber,
anterior and posterior coeloms and right and left atria.
The form of the right pharyngeal chamber of the two mitrates studied shows
that it must have arisen in ontogeny as an outpouching from the left pharyngeal
chamber, which implies that right gill slits probably appeared later in ontogeny
than left gill slits, as they do in the ontogeny of amphioxus.
The form of the posterior coelom of the two mitrates studied suggests that it
arose as an outpouching from the left pharyngeal chamber. Its presumed mode
of origin is comparable with that of a tunicate epicardium.
The oesophagus of M. i. miloni probably opened into the left pharyngeal chamber
near the median line of the theca.
d. The stem
The stem of Calcichordata is interpreted by analogy with the stem of a living
crinoid. Both are compared with the tail of a living chordate, with the following
suggested homologies: chambered organ = notochord, peduncular nerve = dorsal
nerve cord, haemal strand broadly = caudal vessels, aboral nerve centre = brain,
aboral nerves to the theca broadly = cranial nerves. In all known Calcichordata the
stem has an anterior part that flexed mainly to right or left, a posterior part that
flexed mainly in a vertical plane, and a medial part that included a massive element
(dorsal styloid in mitrates, ventral stylocone in cornutes). A massive element of
this sort must, however, have been lacking in the hypothetical transitional form
between cornutes and mitrates.
The posterior stem of cornutes was fundamentally adapted for flexing upwards,
and so consists of imbricating dorsal plates and massive ventral ossicles. The
posterior stem of mitrates was fundamentally adapted for flexing downwards, so
it consists of imbricating ventral plates and massive dorsal ossicles.
The posterior stem of the two cornutes particularly studied reveals direct evidence
of segmented muscle blocks, notochord (= chambered organ) and, probably, paired
segmental blood vessels. The posterior stem of the two mitrates studied reveals
evidence of dorsal and ventral segmental muscle blocks, notochord, dorsal nerve
WITH ECHINODERM AFFINITIES 335
cord and paired segmental ganglia connected to the dorsal nerve cord and located
between muscle blocks. There was probably also a vessel, running down the middle
of the notochord, that sent off vessels laterally and dorsally to the muscle blocks,
and there was probably a dorsal, longitudinal vessel.
Prof. Ubaghs' comparison between the stem of cornutes and mitrates and the
arm of an asteroid must be mistaken since: i. The plates here held to be dorsal in
cornutes and ventral in mitrates, which Ubaghs regards as homologous and repre-
senting cover plates, are ill adapted to open outwards, particularly in the cornute
Cothurnocystis curvata and the mitrate Mitrocystella banandei. 2. If the mutual
orientation of cornutes and mitrates here adopted is correct, then Prof. Ubaghs
must be mistaken, because in neither group can the impressions on the internal
surfaces of the ossicles (ventral in cornutes, dorsal in mitrates) represent the outside
of a water vascular system. This mutual orientation depends mainly on the dis-
position of the thecal chambers.
e. The brain and cranial nerves
The brain of the two cornutes studied is at the anterior (proximal) end of the stem,
like the aboral nerve centre of crinoids. It can be shown to give rise anteriorly to
paired median-line nerves, which go under the rectum, and to paired pyriform
bodies. The median-line nerves may correspond to the nerves n0 of mitrates.
The pyriform bodies correspond to the like-named bodies of mitrates. Two upward
protrusions of the anterior coelom into the pharynx of C. elizae may have carried
the peripheral ends of optic nerves (n3 of mitrates) near the dorsal side of the theca.
In addition to these features, much more of the cranial nerve complex of mitrates
may have been represented by homologous nerves in cornutes but if so, these did
not touch the skeleton.
The brain and cranial nerves of the two mitrates studied were extremely complex
and fundamentally fish-like in plan. The brain had an anterior, a medial and a
posterior part, equivalent respectively to telencephalon, diencephalon plus optic
lobes, and medulla plus ventral mesencephalon. The medial part of the brain
had an upper, optic portion, and a lower hypophyseal portion. From the posterior
part of the brain, paired posterior part nerves (medullary nerves) went off. From
the medial part, paired medial part nerves (optic nerves) went off. Medial and
posterior part nerves probably joined on each side to form the paired palmar nerves,
which must have communicated laterally with the paired pyriform bodies. They
gave rise peripherally to paired nerves n1 to n5, which, with the palmar nerves,
constitute the palmate complexes.
Other important features of the cranial nerves of the mitrates studied were the
peripheral canals of M. i. miloni, the corresponding peripheral grooves of M. mitra,
the paired olfactory openings to the buccal cavity, the lateral-line ganglion which
communicated with the lateral line and was situated just behind the right pyriform
body, and paired nerves n0, near the median line.
By analogy with cephalaspids, which are here interpreted according to Lindstrom
(1949), nerves nx of the palmate complexes probably represent the mandibular
trigeminal nerves of agnathans; nerves n2 represent the maxillary trigeminal nerves
336 PRIMITIVE FOSSIL CHORDATES
of agnathans; nerves n3 represent the optic nerves; nerves n4 and n5, which innervate
the probably sensory peripheral canals or grooves, may possibly represent the
sensory field nerves of cephalaspids. The pyriform bodies are probably homologous
with the trigemino-profundus ganglia of agnathans. The olfactory system of M. i.
miloni and M. mitra resembled that of Heterostraci and gnathostomatous fish
rather than that of cephalaspids. The nerves n0 may possibly represent the hyo-
mandibular branches of the facial nerves of agnathans.
The optic system of M. i. miloni was in all its parts degenerate compared with
that of M. mitra, whose optic nerves (n3) ended peripherally in little bulbs external
to the skeleton, i.e. eyes.
f. Posture and habits
The two cornutes studied habitually lay on the ventral side, as suggested by
previous authors. They probably pulled themselves backwards by sideways
movements of the stem. C. elizae was a deposit feeder and C. curvata a suspension
feeder.
The two mitrates studied also lay habitually on the ventral side, which most
previous authors have regarded as uppermost. They probably pulled themselves
backwards by ventral flexing of the stem, and may also have been able to swim
forwards by lateral flexing of the stem.
g. Definition of Subphylum Calcichordata (Jefferies 1967)
= Class Stylophora (Gill & Caster 1960)
Primitive chordates with a skeleton made of calcite plates, each of which is a
single crystal. Animal clearly divided into a stem and a theca (tail and body).
Stem ending abruptly, with a vertically flexing posterior part, a laterally flexing
anterior part and an abrupt posterior end, perhaps indicating larval attachment by
the stem. Gill slits present, either internal or external, either confined to the left
side, or paired. Mouth at anterior end of theca. Buccal cavity, pharynx, anterior
and posterior coeloms, and sometimes other chambers, recognisable in the theca.
Brain at anterior end of stem, giving rise to paired pyriform ganglia and sometimes
a complex of cranial nerves anteriorly. Stem with notochord and muscle blocks,
and sometimes demonstrably provided with dorsal nerve cord and segmental ganglia.
Stratigraphical range: Middle Cambrian to Devonian.
Formal definitions of the orders Cornuta and Mitrata would at present be pre-
mature.
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EXPLANATION OF PLATES
All illustrated specimens of Cothurnocystis elizae and C. curvata are from the
Starfish Bed, Ashgill Series, Girvan, Scotland. All Mitrocystella incipiens miloni
are from the Schists a Calymenes (Llandeilo Series), Grand Champ de Traveusot,
Traveusot, Ille-et-Vilaine, France. The horizons and localities of Mitrocystella
incipiens incipiens, M. barrandei and Mitrocystites mitra are given for each specimen.
Standard plate and ventral spike notations e.g. MILD, DOL, SIL are not explained
in the captions.
A = Sedgwick Museum, E = British Museum (Natural History), GSM = Geolo-
gical Survey Museum, IG = Institut de Geologic, Rennes, MCZ = Museum of
Comparative Zoology, Harvard, NM = Narodni Museum, Prague.
GEOL. l6.6. 31
PLATE i
Cothurnocystis elizae
FIG. i. E 23137. Latex cast showing interior of gill slits, au = anterior u-plate ; f = flap;
pu = posterior u-plate ; rp = reniform process.
FIGS. 2, 3. E 23157. Latex casts of dorsal and ventral surfaces of juvenile, an = anus ;
cp = crestal plate ; stc = stylocone ; str = strut.
FIGS. 4, 5, 6. E 23394. Ventral, dorsal and oblique lateral aspects of latex casts. Note
variation in form of ventral stem ossicles in fig. 4, anterior points on ventral spikes in fig. 6.
lap = left appendage ; loap = left oral appendage ; rbcr = ridge posterior to buccal cavity
on right ; roap = right oral appendage ; stc = stylocone ; vo = ventral ossicle without boss ;
vob = ventral ossicle with boss.
FIG. 7. E 28657. Latex cast. Dorsal aspect. Note contrast between plates of dorsal
integument in the " foot " region generally, in the region just posterior to the branchial slits
and in the " ankle " region, adp = antero-dorsal process ; dp = dorsal plate ; f = flap ;
rbcr = ridge posterior to buccal cavity on right.
FIG. 8. E 23179. Latex cast. Dorsal aspect showing branchial slits. The flaps indicated f
have been slightly displaced after death relative to the posterior u-plate.
FIG. 9. E 23352. Latex cast. Anterior aspect of internal surface of posterior marginals
cf. Text-fig. 3E. 2 = point on pharyngo-visceral line (pvl), cf. Text-fig. 4d. pco = posterior
coelom.
FIG. 10. E 23705. Latex cast. Dorsal surface. Large individual with circular plates in
the dorsal integument of the " ankle " as well as " foot " region, an = anus ; if = imbrication
flap of ventral plate of anterior stem.
Bull. Br. Mus. nat. Hist^(Geol.) 16,6
~
PLATE i
10
GEOL. 16, 6.
PLATE 2
Cothurnocystis elizae
FIGS, i, 5, 6, 7. E 28644. Natural mould, ventral aspect, pco = posterior coelom ; rbcr
= ridge behind buccal cavity on right ; rg = rectal groove. 5, oblique right aspect, ventral
side upwards. 6, cast of cerebral basin. 7, posterior coelom, posterior aspect. 4/5, 5, points
on pharyngo-visceral line, cf. Text-fig. 40. mini = left median line nerve ; nmln = notch for
median-line nerves ; pbl — left pyriform body ; pbr = right pyriform body ; pco = posterior
coelom ; pvl = pharyngo-visceral line ; rbcr = ridge (on skeleton) delimiting buccal cavity
posteriorly on right ; rg = rectal groove (on skeleton) ; sp = striations of pharynx.
FIG. 2. E 28667. Natural mould. Postero-ventral aspect, ventral side upwards. Cf.
Text-fig. 4d. i, 1/2, 3, 3/4, 4, 4/5 — points on pharyngo-visceral line. For other letters see
explanation to fig. i, etc.
FIG. 3. E 28660. Latex cast, dorsal aspect, acp = area of circular plates in anterior, left,
ventral integument ; rbcr = ridge behind buccal cavity on right.
FIG. 4. E 23723. Latex cast. Ventral aspect. Juvenile specimen ; spikes all ill-developed
except SB which is lateral instead of ventral ; articulation at base of right oral appendage
(roap) visible, mo = mouth.
FIG. 8. E 28639. Latex cast. Antero-dorsal aspect of inside of theca just anterior to stem.
Cf. Text-fig. 3b. gmln = groove for median-line nerve ; hf = horizontal flange of MIR+LV;
nmln — notch for median-line nerves ; pbd = depression for pyriform body ; rg = rectal
groove ; rpc = ridge delimiting posterior coelom.
FIG. 9. E 23705. Latex cast. Dorsal aspect of ventral ossicles of posterior stem. Cf.
Text-fig. 6. dp = dorsal plate (fragment) ; fdp = facet for dorsal plate ; Ipt = lateral pit ;
mg = median groove ; tg = transverse groove.
Bull. Br. Mus. nat. Hist. (Geol.) 16, 6.
PLATE 2
GEOL. l6, 6,
PLATE 3
Cothurnocystis elizae
FIG. i. E 28639. Latex cast. Dorsal aspect to show right and left internal ridges
delimiting the posterior margin of the buccal cavity (rbcl, rbcr). str = strut.
Cothurnocystis curvata
FIGS. 2, 3, 6. E 28652. 2, dorsal aspect. 3, ventral aspect. 6, anterior aspect. Cf. Text-
figs, ya, b, c. bs = branchial slit ; lap = left appendage ; mo = mouth ; pco = posterior
coelom ; rbcl, rbcr = ridges delimiting buccal cavity on left and right sides ; str = strut.
FIG. 4. E 28662. Dental rubber cast. Ventral aspect of branchial complex. Cf. Text-
fig. 9. aep = anterior excavate process ; arc = arcuate canal, formed from apposed arcuate
grooves ; pep = posterior excavate process ; vg — ventral groove ; y — point where neigh-
bouring chevrons touch each other, ventral to the arcuate canal.
FIG. 5. E 28652. Latex cast. Same specimen as figs. 2, 3, 6. Dorsal aspect of posterior
coelom, the roof of which is incomplete. Cf. Text-fig, zoa.
FIG. 7. E 28551. Latex cast. Ventral aspect. Specimen shows right and left appendages
(rap, lap) and supernumary ventral spike (San).
FIG. 8. E 23168. Latex cast. Posterior aspect. Cf. Text-fig. lie.
FIG. 9. GSM 60839. Natural mould. Note distal rectal canal (drc) leaving rectal groove
(rg) and opening near the most median branchial slits, bs = branchial slit ; pco = posterior
coelom. The branchial skeleton and dorsal integument are represented by moulds of their
external surfaces.
FIG. 10. E 28650. Latex cast. Dorsal aspect of anterior stem and region in front of it
to show absence of external anus, bs = branchial slit.
Bull. BY. Mus. nat. Hist. (Geol.) 16, 6.
PLATE 3
PLATE 4
Cothurnocystis curvata
FIGS, i, 4. E 28661. Dental rubber cast of posterior stern, i, right aspect ; 4, dorsal
aspect. Cf. Text-fig. 12. admp = admedian process ; afc — anterior facet ; dp = dorsal
plate ; mg = median groove ; tb = transverse buttress ; tg = transverse groove. Arrows
point towards theca.
FIGS. 2. 3. E 28656. Natural mould of region of buccal cavity, ventral side downwards, to
show sculpture on internal mould of theca. 2, left aspect. 3, right aspect, be = buccal
cavity ; liaf = lower integument attachment facet ; uiaf = upper integument attachment
facet.
FIGS. 5, 6. E 28572. Natural mould of inside of theca, to show superficial internal sculpture.
Ventral side upwards. Cf. Text-fig. 10. 5, posterior aspect. 6, left aspect, ph = pharynx ;
liaf = upper integument attachment facet ; uiaf = lower integument attachment facet.
FIG. 7. E 28893. Natural mould of internal cast, anterior aspect. Cf. Text-fig. loa.
liaf = lower integument attachment facet ; ph = pharynx ; uiaf = upper integument attach-
ment facet ; str = strut.
Mitrocystella incipiens miloni
FIG. 8. IG 90. Latex cast. Ventral surface, or = oral plate ; tr = transverse ridge-
MIBV, first right ventral marginal.
FIGS. 9, 10. M. i. miloni. E 23665. Dental rubber cast. 9, posterior aspect. 10, right
aspect, ng — narrow groove (lateral line).
Bull. Br. Mus. nat. Hist. (Geol.) 16,6.
PLATE 4
PLATE 5
Mitrocystella incipiens miloni
FIGS, i, 4. IG 1 8. Natural mould, i, dorsal, 4, posterior aspect, gpco = groove limiting
posterior coelom ; grp = groove limiting right pharyngeal chamber ; la = left atrium ; Iph =
left pharyngeal chamber ; na — nerve n2 of palmar complex ; pal = base of palmar nerve ;
pco = posterior coelom ; rb = rectal bridge ; rr = rectal ridge.
FIG. 2. 1030. Latex cast of dorsal surface. Note calcite cleavage cracks (ccc).
FIGS. 3, 6. IGno. Natural mould. 3, left posterior part of theca, dorsal aspect. 6, right
posterior part of theca, postero-ventral aspect, dorsal side upwards, af = anterior furcation
of palmate complex ; csb = carrot-shaped body (lateral-line ganglion) ; e — vestigial eye ;
nL_5 = nerves of palmate complex ; pal = palmar nerve ; pb = pyriform body ; pc = peri-
pheral canal ; pf = posterior furcation of palmate complex.
FIG. 5. IG 348. Latex cast of posterior stem. Left aspect, ia = interossicular articu-
lation ; do = dorsal ossicle ; vp = ventral plate ; x = point where ventral plate overlaps
dorsal ossicle.
FIG. 7. E 28887. Natural mould. Dorsal aspect of anterior part to show buccal cavity
(be) as it appears before dissection cf. fig. 9. na = nerve of palmar complex ; og = oblique
groove ; olo = olfactory opening.
FIG. 8. IG 70. Natural mould. The surface shown is a cast of the inside of the external
layer of plate MIRV- af = anterior furcation of palmate complex ; csb — broken-off carrot-
shaped body (lateral-line ganglion) ; nx_6 = nerves of palmate complex ; pal = palmar
nerve ; pf = posterior furcation of palmate complex ; pb = pyriform body ; tol = cast of
thickening of outer layer of calcite.
FIG. 9. E 23664. Natural mould. Dorsal aspect of anterior part with buccal cavity partly
dissected out. Cf. fig. 7. For legend see fig. 7.
Fig. 10. E 23664. Dental rubber cast, representing dorsal posterior skeleton of theca,
ventral aspect. To show nature of separation (llpc) between posterior coelom (pco) and left
pharyngeal chamber (Iph). obr = oblique ridge ; pb = cupule for pyriform body ; rpco =
ridge limiting posterior coelom.
Fig. ii. IGgi. Natural internal mould, ventral aspect of right posterior part, gpco =
groove limiting posterior coelom ; n0 = nerves n0 ; nx_3 = grooves representing nerves of
palmate complex ; MIRV = first right ventral marginal plate ; VPM = posterior, median
ventral plate (displaced).
Bull. BY. Mus. nat. Hist. (Geol.) 16,6.
PLATE 5
PLATE 6
Mitrocystella incipiens tniloni
FIG. i. A.462y/a. Natural internal mould, dorsal aspect, posterior part, ap = anterior part
of brain ; e = eye ; Iph = left pharynx ; mp = medial part of brain ; pc = peripheral canal ;
pco = posterior coelom ; pp — posterior part of brain.
Mitrocystella barrandei
FIG. 2. NM Akc Kat 437/65. Sarka Beds, Osek Czechoslovakia. Natural mould of cere-
bral depression representing brain, antero-ventral aspect, dorsal side upwards. Imp = lower
medial part of brain (enclosed in life by hypocerebral processes) ; mpf = medial part foramen ;
pp = posterior part of brain ; ppn = posterior part nerve ; ump = upper medial part of
brain ; w — point of division between Imp and ump.
FIG. 3, 5. E 7517. Sarka Beds, Rokycany, Czechoslovakia. Latex cast. 3, detail of
stem, 5, ventral aspect, as = anterior stem ; do = dorsal ossicle ; ia = interossicular
articulation ; or = oral plate ; vp = ventral plate ; x = point where ventral plate overlaps
dorsal ossicle.
Mitrocystella incipiens miloni
FIG. 4. IG 3. Natural mould representing brain, antero-dorsal aspect, mp = medial
part of brain ; mpf == medial part foramen ; ng = narrow groove (lateral line) ; pb = pyri-
form body ; pp = posterior part of brain ; ppn = posterior part nerve.
Mitrocystites mitra
FIG. 6. MCZ 565. Sarka Beds, Osek. Natural mould, dorsal aspect of posterior part.
la = left atrium ; mp — medial part of brain ; n2, n3, n4+5 = nerves of palmate complex ;
mp = medial part of brain ; og = oblique groove ; pp = posterior part of brain ; ra — right
atrium.
M. i. miloni
FIG. 7. IG 355. Internal cast of MIRD. ccc = calcite cleavage cracks ; pc — peripheral
canal ; sc = short canals across M^R, possibly carrying olfactory fibres.
Mitrocystites mitra
FIG. 8. NM Akc Kat 22011, 1923, 68 1. Hanus Colin. 256. Sarka Beds, Sarka,
Czechoslovakia. Latex cast. Same specimen as PL 10, fig. 4. Dorsal aspect of oral plates.
hg = hmiecylindrical groove ; or — oral plates.
FIG. 9. NM Akc Kat. 22011/1923. Sarka Beds, Sarka. Natural mould of anterior surface
of posterior stem ossicle, aig = anterior interossicular groove ; aiid = anterior inner inter-
ossicular depression ; aoid = anterior outer interossicular depression ; die = dorsal, longitu-
dinal canal.
Mitrocystella incipiens miloni
FIG. 10. IG specimen h. Natural mould of ventral side of a dorsal, posterior stem ossicle
giving representation of original soft structures, dnc = dorsal nerve cord ; gap = ganglionar
process ; Ig = lateral ganglion ; not == notochord ; pig = posterior interossicular groove ;
pogp = post ganglionar process ; z = boundary between dnc and not.
FIG. ii. IG 45. Internal cast of posterior dorsal posterior stem ossicle, right aspect, aiid
= anterior, inner, interossicular depression ; aoid = anterior, outer, interossicular depression ;
die = dorsal longitudinal canal; mg = median groove infilling (= notochord); pig — posterior
interossicular groove ; piid = posterior inner interossicular depression ; poid = posterior,
outer, interossicular depression.
FIG. 12. A 46271 (same individual as in PL 6, fig. i and PL 7, fig. 3). als = anterior
lumen of styloid ; die = dorsal longitudinal canal ; vgls = vertical groove on lumen of styloid.
Bull. Br. Mus. nat. Hist. (Geol.) 16, 6.
PLATE 6
11
PLATE 7
Mitrocystella incipiens tniloni
FIG. i. E 28889. Trace of palmar nerve (pal) on anterior face of posterior coelom.
FIG. 2. IG 48. Natural mould of ventral side of dorsal posterior stem ossicle immediately
behind styloid. Theca right of picture. Iga = left ganglion; rga = right ganglion; ic —
interossicular canal. For other legends see PL 6, fig. 10.
FIG. 3. Internal natural mould of styloid. A 46271. Same specimen as PI. 6, figs, i, 12.
ic = interossicular canal between fused ossicles of styloid ; Ig — lateral groove ; pig — posterior
interossicular groove ; piid = posterior inner interossicular depression ; poid = posterior
outer interossicular depression.
Mitrocystites tnitra
FIG. 4. Same specimen as PL 6, fig. 9. Internal mould of M2L ; on3 — opening of n3 on
to dorsal surface ; si = excavation in skeleton for soft layer of skeleton.
Mitrocystella incipiens incipiens
FIG. 5. MCZ 580. Sarka Beds, Svata Dobrotiva, Czechoslovakia. Internal mould of
posterior stem, die = dorsal longitudinal canal ; gmb = groove separating muscle blocks ;
iid = infilling of interossicular depression ; not = notochord ; oid = outer, interossicular
depression.
Mitrocystella incipiens tniloni
FIG. 6. IG 48. Natural internal mould, posterior part, left-dorsal aspect, og — oblique
groove ; sll = infilling of excavation in skeleton for reception of lateral extensions of ventral
soft layer ; sip = the same for posterior extensions of ventral soft layer.
Bull. Br. Mus. nat. Hist. (Geol.) 16, 6.
PLATE 7
PLATE 8
Mitrocystites tnitra
FIG. i. E 16062. Sarka Beds, Osek, Czechoslovakia. Dental rubber cast, dorsal aspect.
dn3 = depression at end of nerve n3 (optic depression) ; do = dorsal ossicle ; ia = interossi-
cular articulation ; Ip = lateral pore ; pg = peripheral groove ; on3 — opening of nerve n3
on to dorsal surface ; std = styloid.
FIGS. 2, 4, 6. MCZ 566. Sarka Beds, Osek. Dental rubber casts. 2, dorsal aspect of
MILV- 4> ventral aspect of posterior left, dorsal skeleton. 6, antero-ventral aspect of the
same, dorsal side upwards, af = articular facet ; bo = branchial opening ; bsl = break in
slope anterior to af ; gmpn = groove for medial part nerve ; hep = hypocerebral process ;
il = inner layer of skeleton ; la = left atrium ; mpf = medial part foramen ; obr = oblique ridge ;
ol = outer layer of skeleton ; pb = cupule for pyriform body ; rpc = ridge delimiting pos-
terior coelom ; sl(n4+5) = cavity for soft layer of skeleton carrying nerves n4 and n5.
FIG. 3. NM Akc Kat 22011/1923, Inv. no. 511, Sarka Beds, Sarka. Latex cast. Ventral
aspect of posterior part of theca. ng = narrow groove (lateral line) ; bo = branchial opening.
FIG. 5. NM Akc Kat 22011/1923 Hanus Collection no. 354 +. Latex cast. Ventral aspect
of dorsal skeleton. Juvenile specimen showing fenestrated calcite and leftward facing mouth,
ceb = cerebral basin ; obr = oblique ridge ; olo = olfactory opening.
FIGS. 7, 9. E 16067. Sarka Beds, Osek. Natural mould of cerebral basin representing
brain. 7, anterior aspect. 9, right aspect, ap = anterior part ; mp = medial part ; pp =
posterior part ; ppn = posterior part nerve.
FIG. 8. NM Barrande Collection. Osek. Latex cast, ventral aspect, or = oral plate ;
por = post oral plate.
FIG. 10. MCZ. 567. Natural internal mould, dorsal aspect. The specimen has been
encrusted by a branching epizoan. la = left atrium ; mb = median branch of oblique groove ;
mp = medial part of brain ; n2 = main trunk of nerve n2, 112 A — anterior branch of nerve n2 ;
ns = nerve n3 (optic nerve) ; og = oblique groove ; olo = olfactory opening ; pp — posterior
part of brain ; rr = rectal ridge ; tr = transverse ridge.
Bull. Br. Mus. nat. Hist. (Geol.) 16,6.
PLATE 8
PLATE 9
Mitrocystella incipiens miloni
FIG. I. E 28886. Natural internal mould, dorso-posterior aspect of right half, af =
articular facet of MIRD ; csb = carrot-shaped body (lateral-line ganglion) ; gpco = groove
limiting posterior coelom ; mpf = medial part foramen ; n5 = nerve n5 of palmate complex ;
pb = pyriform body ; ra = right atrium ; sip = posterior extension of soft layer into dorsal
skeleton.
FIG. 2. IG 18. Same specimen as PI. 5, figs. 1,4. Latex cast showing oblique ridge near
median branch (mb). Between the median branch and the point v, the oblique ridge was
probably in contact with the anterior opening of the oesophagus.
Mitrocystella incipiens incipiens
FIG. 3. Same specimen as PL 7, fig. 5, but more posterior. Pyritous internal mould of
posterior stem, die = dorsal longitudinal canal ; fdo — fragments of dorsal ossicle ventral
to me ; ic = interossicular canal ; id = infilling of Pinner interossicular depression ; Ibv =
lateral blood vessel ; me = infilling of median canal (notochord).
FIG. 4. IG 45d. Natural mould of external surface of Mmv and MIRD showing cruciform
lateral line (narrow groove = ng) and part of lateral-line ganglion (carrot-shaped body = csb).
Mitrocystites mitra
FIG. 5. MCZ. 568. Sarka Beds, Osek, Czechoslovakia. Natural mould of ventral surface
of dorsal ossicles of posterior stem, giving a representation of the soft parts, dnc = dorsal
nerve cord ; dvf = dorso-ventral facet, for reception of ventral plate ; ic = interossicular canal ;
Iga = lateral ganglion ; not = notochord ; pig = infilling of posterior, interossicular groove.
FIG. 6. NM Akc Kat 32417/1950. Sarkd Beds, Osek. Latex cast of cerebral basin, pos-
terior aspect. Imp = part of basin carrying lower medial part of brain, i.e. inside of hypo-
cerebral processes ; mpf = medial part foramen ; pp = part of basin carrying posterior part
of brain ; ump = part of basin carrying upper medial part of brain ; w = blunt ridge on
skeleton separating ump from Imp (cf. Text-fig. 27b, c, PL 6, fig. 62).
Bull. Br. Mus. nat. Hist. (Geol.) 16, 6.
PLATE 9
PLATE 10
Mitrocystella incipiens miloni
FIG. i. E 28888. Note striations (sp) on left pharyngeal chamber, grp = groove limiting
right pharyngeal chamber ; n2 — nerve n2 ; pco = posterior coelom ; si = soft layer of
dorsal skeleton.
FIG. 2. IG 53. Natural mould. Left dorsal aspect to show typical posture with theca
horizontal and posterior stem bent ventralwards. als = anterior lumen of styloid ; as =
anterior stem ; ps = posterior stem.
FIG. 3. St. Andrews University, MacGregor Colin. T.3. Natural internal mould of pos-
terior portion of theca, dorsal aspect, csb = carrot-shaped body (lateral-line ganglion) ;
csbn — nerve to csb ; n6, = nerve of palmate complex ; og = oblique groove ; mp — medial
part of brain ; sip = posterior extension of soft layer into dorsal skeleton.
Mitrocystites mitra
FIG. 4. Same specimen as PI. 6, fig. 8. Dorsal aspect of most of ventral and part of dorsal
skeleton, il = inner layer of ventral skeleton ; ol = outer layer of ventral skeleton.
FIG. 5. MCZ 566. Sarka Beds, Osek, Czechoslovakia. Latex cast. Dorsal aspect of
posterior, dorsal skeleton. Shows finer surface ornament in region of peripheral grooves (pg)
than elsewhere. Ip = lateral pore ; on3 = opening of n3 on to dorsal surface ; tr = transverse
ridge.
FIG. 6. E 16058. Sarka Beds, Osek. Natural internal mould of dorsal skeleton, dorsal
aspect. Note especially striations of right pharyngeal chamber (sp) and groove (grp) limiting
right pharyngeal chamber on the median side, la = left atrium ; mb = median branch of
oblique groove; mp = medial part of brain; n2, n3, n5, n4+5 = nerves of palmate complex ;
pco = posterior coelom ; pp = posterior part of brain ; rr — rectal ridge ; tr — transverse
ridge.
FIG. 7. E 15017. Sarka Beds, Osek. Latex cast. Dorsal aspect to show stem flexed to
right, probably in a fairly natural position, as = anterior stem ; Ip = lateral pore ; on3 =
opening of nerve n3 on to dorsal surface ; pg = peripheral groove ; ps = posterior stem.
FIG. 8. Same specimen as in PI. 10, fig. 6. Internal mould of posterior part of ventral
skeleton, csb = carrot-shaped body (lateralis ganglion) ; gpco = groove limiting posterior
coelom ; n3 = nerve n3 of palmate complex in ventral skeleton ; pb = pyriform bodies (damaged
in dissection) ; si — soft layer of ventral skeleton.
Bull. Br. Mus. nat. Hist. (Geol.) 16,6.
PLATE 10
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AUSTRALIENS UND KANADAS UND
AUS DEM MITTELDEVON
SPITZBERGENS
HANS-PETER SCHULTZE
BULLETIN OF
THE BRITISH MUSEUM (NATURAL HISTORY)
GEOLOGY Vol. 16 No. 7
LONDON: 1968
PAL^EONISCOIDEA-SCHUPPEN AUS DEM
UNTERDEVON AUSTRALIENS UND KANADAS
UND AUS DEM
MITTELDEVON SPITZBERGENS
BY
HANS-PETER SCHULTZE
Pp. 341-368; 4 Plates; 19 Text-figures
BULLETIN OF
THE BRITISH MUSEUM (NATURAL HISTORY)
GEOLOGY Vol. 16 No. 7
LONDON: 1968
THE BULLETIN OF THE BRITISH MUSEUM
(NATURAL HISTORY), instituted in 1949, is
issued in five series corresponding to the Departments
of the Museum, and an Historical series.
Parts will appear at irregular intervals as they become
ready. Volumes will contain about three or four
hundred pages, and will not necessarily be completed
within one calendar year.
In 1965 a separate supplementary series of longer
papers was instituted, numbered serially for each
Department.
This paper is Vol. 16, No. 7 of the Geological
(Palaeontological) series. The abbreviated titles of
periodicals cited follow those of the World List of
Scientific Periodicals.
World List abbreviation
Bull. Br. Mus. nat. Hist. (Geol.).
Trustees of the British Museum (Natural History) 1968
TRUSTEES OF
THE BRITISH MUSEUM (NATURAL HISTORY)
Issued 13 August, 1968 Price £i 6s.
PAL^ONISCOIDEA-SCHUPPEN AUS DEM
UNTERDEVON AUSTRALIENS UND KANADAS
UND AUS DEM MITTELDEVON SPITZBERGENS
By HANS-PETER SCHULTZE
SYNOPSIS
Zwei neue Gattungen und Arten (Dialipina salgueiroensis und Ligulalepis toombsi) der
Palaeoniscoidea aus dem Unterdevon von NW-Kanada und SE-Australien sind beschrieben.
Von diesen Formen sind nur Schuppen bekannt; diese Schuppen zeigen Merkmale, die von
anderen Palaeoniscoidea nicht bekannt sind. AuBerdem sind Schuppen von Orvikuina sp.
aus dem Mitteldevon (Grey Hoek Schichten) von Spitzbergen beschrieben. Der unregelmaBige
Verlauf der Williamson 'schen Kanale in den Schuppen von Orvikuina und Dialipina ist dis-
kutiert. Alle Schuppen sind in Schichten marinen Ursprungs gefunden worden.
Two new palaeoniscoid genera and species-Dialipina salgueiroensis and Ligulalepis toombsi-
are described from Lower Devonian rocks of Northwestern Canada and Southeastern Australia.
These forms are represented only by scales which show certain characters hitherto unknown in
Palaeoniscoidea. In addition scales of Orvikuina sp. are described from the Middle Devonian
(Grey Hoek beds) of Spitsbergen. The irregular canals of Williamson in the scales of Orvikuina
and Dialipina are discussed. The forms described here occur in marine rocks.
CONTENTS
Seite
I. EINLEITUNG .......... 343
II. MORPHOLOGIE UND HlSTOLOGIE ...... 345
Ligulalepis nov. gen ........ 345
Ligulalepis toombsi gen. et sp. nov. . . . . . 345
Dialipina nov. gen. . . . . . . . 351
Dialipina salgueiroensis gen. et sp. nov. . . . . 352
Orvikuina sp. ......... 357
III. DlSKUSSION ZUR HlSTOLOGIE ....... 363
IV. STRATIGRAPHIE UND FAUNA ....... 365
V. SUMMARY .......... 366
VI. ZlTIERTE LlTERATUR ........ 367
I. EINLEITUNG
Die altesten Palaeoniscoidea sind aus dem Mitteldevon bekannt, so ist von Interesse,
aus dem Unterdevon auch Reste allein zu beschreiben. Die hier beschriebenen
Palaeoniscoidea-Schuppen stammen von weit auseinanderliegenden Fundpunkten,
einmal aus SE-Australien, dann aus NW-Kanada. Hinzugefiigt sei eine Beschrei-
bung von Schuppen aus dem Mitteldevon Spitzbergens, die der Gattung Orvikuina
angehoren und bisher nur aus dem baltischen Mitteldevon bekannt waren.
Die Bearbeitung des Materials erfolgte im Naturhistoriska Riksmuseet, Paleo-
zoologiska sektionen, Stockholm. Aufbewahrt werden die Schuppen aus Australien
im British Museum (Natural History), London, die Schuppen aus Kanada im
National Museum of Canada, Ottawa und die Schuppen aus Spitzbergen im Natur-
historiska Riksmuseet, Paleozoologiska sektionen, Stockholm (nicht in Essigsaure
aufgelostes Gestein der gleichen Lokalitat besitzen das British Museum (Natural
History), London und das Paleontologiska Museum, Oslo).
GEOL. l6, 7. 32
344 PAL^ONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON
Alle Schuppen wurden durch Herauslosen mit Essigsaure aus dem Gestein gewon-
nen. Von dem australischen Material lagen nur die isolierten Schuppen zur
Bearbeitung vor (herausgelost am British Museum (Natur. Hist.), London), dagegen
von dem Material aus Kanada und Spitzbergen (Schuppen herausgelost von Dr. T.
0rvig, Naturhist. Riksmuseet, Stockholm) auch das Gestein. In dem leicht schie-
frigen Gestein aus Kanada ist eine Bearbeitung der Schuppen auch ohne Herauslosen
moglich. Fur die Diinnschliffe wurden die isolierten Schuppen in eine Plastikmasse
eingebettet (Soredur H 75 von der Firma Svenska Oljeslageri Aktiebolaget, Gote-
borg). Zusatzlich wurden von dem Material aus Spitzbergen und Kanada Schliffe
von Schuppen angefertigt, die noch im Gestein saBen.
Die Schuppen wurden mit einer wasserloslichen Farbe griin gefarbt und mit
Ammoniumchlorid bestaubt, bevor sie photographiert wurden. Die Aufnahmen
habe ich selbst gemacht, die Abziige davon Herr W. Wetzel, der Photograph des
Geol.-Palaont. Instituts Tubingen. Die Zeichnungen wurden von Herrn C. Sal-
gueiro, Naturhist. Riksmuseet, Stockholm angefertigt.
Fur die jederzeit groBziigige Unterstiitzung im Naturhistoriska Riksmuseet,
Paleozoologiska sektionen, Stockholm mochte ich dem Direktor Herrn Professor
Dr. E. Jarvik herzlich danken. Besonders stark hat Intendent Dr. T. 0rvig diese
Arbeit gefordert, er hat mir das Material aus Kanada und aus Spitzbergen zur
Verfiigung gestellt. Viele Angaben im stratigraphischen Teil dieser Arbeit verdanke
ich ihm. Das australische Material sandte Dr. C. Patterson nach Stockholm, die
Erlaubnis zur Bearbeitung erteilte Dr. E. I. White, beide British Museum (Natur.
Hist.), London. Mr. H. A. Toombs, British Museum (Natur. Hist.), London war so
freundlich, mir ein ausfuhrliches Verzeichnis der australischen Fundpunkte zu
schicken. Professor Dr. W. Gross, Geol.-Palaont. Institut, Tubingen, war so
entgegenkommend, mir Schliffe von Orvikuina aus Spitzbergen zur Bearbeitung zu
iiberlassen, die er friiher selbst hergestellt hatte.
Fur die Anfertigung der Zeichnungen habe ich Herrn C. Salgueiro, Naturhist.
Riksmuseet, Paleozool. sektionen, Stockholm sehr zu danken. Eingefiihrt in das
oben beschriebene Photographierverfahren hat mich Dr. F. Adamczak, Geologiska
institutionen der Universitat Stockholm. Fur die Herstellung der Abziige danke
ich Herrn W. Wetzel, Geol.-Palaont. Institut Tubingen. Dr. G. J. Nelson, American
Museum, New York hat freundlicherweise die englische Zusammenfassung korri-
giert.
Mein Aufenthalt in Stockholm wurde von der Deutschen Forschungsgemeinschaft
nnanziert.
Benutzte Abkiirzungen :
BM British Museum (Natural History), London
GrB Schliffsammlung W. Gross aus dem Institut fur Palaontologie und
Museum Berlin
NMC National Museum of Canada, Ottawa
PMO Paleontologiska Museum, Oslo
Sto Naturhistoriska Riksmuseet, Paleozoologiska sektionen, Stockholm
•<- zeigt in den Abbildungen immer in rostraler Richtung
PAI^EONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON 345
II. MORPHOLOGIE UND HISTOLOGIE
LIGULALEPIS nov. gen.
DEFINITION. Gattung der Palaeoniscoidea mit hohen Schuppen an den Flanken ;
Schuppen nahe dem Schultergiirtel 3-4 mal so hoch als lang; an der vorderen
oberen Ecke ein sehr markanter Fortsatz, der vom Vorderrand1 scharfwinkelig
abgesetzt ist; Ventralrand vom Vorderrand schrag nach caudal abfallend. Kraf-
tiger Dorn und dementsprechend tiefe Grube; Kiel recht tief; zweiter " Kiel ", an
dessen Hinterrand die Offnungen der meisten Kanale liegen.
DERIVATIO NOMINIS. ligula (lat.) = flacher Loffel (bezieht sich auf den Fortsatz
an der vorderen oberen Ecke), Aem? (griech.) = Schuppe.
Ligulalepis toombsi gen. et sp. nov.
(Abb. 1-6, Taf. I, Fig. 1-8 u. Taf. IV, Fig. i)
DEFINITION. Als Artmerkmale seien der Gattungsdefinition vor allem die
Ausbildung der Ganoinflache hinzugefiigt. Ganoinflache stark gegliedert, zurn
Ventralrand hin teilweise in einzelne Rippen zerteilt, zum Vorderrand hin mit
Langsleistchen verziert und in einzelne Schiippchen aufgelost ; Hinterrand pectinat ;
Vorderrand gerade oder schwach konkav, vordere untere Ecke abgerundet, Ventral-
rand gerade.
FUNDSCHICHT/-ORT. Taemas Stufe, Murrumbidgee Schichten, Unterdevon/Mur-
rumbidgee River, New South Wales, Australien2.
MATERIAL. 202 Schuppen und Schuppenbruchstiicke, 6 Schliffe.
HOLOTYP. BM: P 48864 (Abb. i u. Taf. I, Fig. 4).
DERIVATIO NOMINIS. toombsi = zu Ehren von H. A. Toombs, der die hier
beschriebenen Fossilien 1963 in New South Wales gesammelt hat.
STRATIGRAPHIE. Bei der Essigsaurepraparation der Vertebratenfossilien3 die
H. A. Toombs 1963 in der Umgebung des Murrumbidgee Rivers gesammelt hatte,
kamen in den Riickstanden auch kleinere Reste von Vertebraten (" Vertebraten-
Mikrofossilien ") zum Vorschein, darunter auch die Schuppen von Palaeoniscoidea.
Diese Palaeoniscoidea-Schuppen aus dem Unterdevon sind alter als alle bisher
beschriebenen Palaeoniscoidea, Palaeoniscoidea sind erst ab dem Mitteldevon
bekannt (Orvikuina, Cheirolepis). Friiher wurden auch die australischen Schichten
ins Mitteldevon gestellt, diese Einstufung stellte sich aber bei Uberpriifung der
Invertebratenfauna als unrichtig heraus (Philip, G. M. u. Pedder, A. E. M. 1964).
Die Conodontenfauna der etwa gleichaltrigen Schichten im Buchan District stuft
G. M. Philip 1967 ins untere Emsium ein, in derselben Arbeit stellt er die Murrum-
1 Begriffe benutzt wie in Schultze, H.-P. 1966, Abb. i, S. 236.
2 detaillierte Angaben bei den Abbildungen nach H. A. Toombs.
3Es handelt sich hauptsachlich um Arthrodiren; diese bearbeitet zur Zeit Dr. E. White (vergleiche
dazu die Beschreibung von Arthrodiren der gleichen Fundstelle, White, E. IQ52)-
346 PAL^ONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON
bidgee Schichten ins obere Emsium (oberstes Unterdevon) . Fiir die Murrumbidgee
Schichten gibt I. Browne 1959 folgende Einteilung:
Taemas Stufe:
Feine Tuflfe und Schiefer
Crinoidenkalk
Warrookalk
Receptaculites Kalk .
Bloomfieldkalk
Currajongkalk .
Spirifer yassensis Kalk
Majurgong Stufe:
Rote Schiefer, Sandsteine
und Quarzite .
Cavan Stufe:
Diinnbankiger Kalk
Gelandestufe bildender Kalk
Plattige Kalke, Schiefer
und Quarzite
Machtigkeit
in feet
100
500
370
590
400
400
400
400
Anzahl an Schuppen
und -bruchstucken
6, ?i
?6
170, ?2
400
insgesamt 202
In dieser Tabelle sind die der Arbeit zu Grunde liegenden Schuppen in ihrer
stratigraphischen Verbreitung aufgefiihrt, fur mit ? versehene Zahlen ist die strati-
graphische Zuordnung fraglich. Der Hauptteil der Schuppen stammt aus dem
Spirifer yassensis Kalk und davon die meisten (108 = 53,5 % aller Schuppen) von
einem Fundpunkt nahe der Basis des Spirifer yassensis Kalkes. UnverhaltnismaBig
haufig sind unter den Schuppen die hohen Schuppen der Flanken vertreten, was
wohl nur auf Auslese bei der Ablagerung beruht. Die eigentlich am Fisch zahl-
reicheren, mehr rhombischen Schuppen der Dorsal-, Ventral- und Caudalregion
sind selten.
MORPHOLOGIE. Die hohen Schuppen zeigen zwei sehr auffallige Merkmale im
Vergleich zu den Schuppen anderer Palaeoniscoidea : einen loffelformigen Fortsatz
an der vorderen oberen Ecke und einen zweiten " Kiel "auf der Innenseite. Vom
geraden Vorderrand biegt an der vorderen oberen Ecke der loffelformige Fortsatz
winkelig ab (Abb. i, 4 u. Taf. I, Fig. 4-6). Wohl ist bei rhombischen Schuppen die
vordere obere Ecke oft verlangert (Taf. I, Fig. 9), bildet aber nie einen derartig
breit abgerundeten Fortsatz. Dieser Fortsatz fehlt den rhombischen Schuppen vor
der Caudalis (Abb. 2 u. Taf. I, Fig. 8), aber auch den besonders hohen Schuppen
direkt hinter dem Schultergiirtel. Diese hohen Schuppen (Abb. 3 u. Taf. I, Fig.
i, 2) besitzen auch keinen deutlich ausgebildeten Dorn. Im Gegensatz zu den
Flankenschuppen, die bis 3 mal so hoch wie lang werden, erreichen diese Schuppen
hinter dem Schultergiirtel bis iiber 4fache Hohe verglichen zur rostral-caudalen
Erstreckung (= Lange).
Der Dorn, recht kraftig ausgebildet, lauft von einer breiten Basis zu einer Spitze
aus (Taf. I, Fig. 5, 6). Er greift in eine tiefe Grube (Abb. ib u. Taf. I, Fig. 4b), die
zwischen Kiel und zweitem " Kiel " liegt. Von der Grube zur Mitte des Domes
PAL^ONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON
347
ABB. i, 2, 3b. Ligulalepis toombsi n.g. n. sp., Unterdevon, New South Wales, Australien.
i. BM: P 48864. Holotyp. Spirifer yassensis Kalk (unterer Teil), "right bank of
Murrumbidgee, boulders probably nearly in situ, on shore and up hillside, 2500 yds. due
E. of Majurgong T.S. " Hohe Schuppe aus der vorderen Korperhalfte der linken
Korperseite. a, AuBenseite. b, Innenseite. x 40. 2. BM: P 48849. Bloomfield
Kalk, " not in situ, on hillside south of inlet, 2750 yds at 4° magnetic from Majurgong
T.S. " Seitenlinienschuppe aus der hinteren Korperhalfte der linken Korperseite. a,
AuBenseite. b, Innenseite. x 40. 3b, BM: P 48853. Spirifer yassensis Kalk (unterer
Teil), Lokalitat wie P 48864 (— Abb. i). Hohe Schuppe aus der Region dicht hinter dem
Schultergiirtel, rechte Korperseite. Innenseite. x 40.
k = Kiel, k' = zweiter " Kiel ", v = vordere und h = hintere Offnung des Seiten-
linienkanals.
348 PAL^ONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON
verlauft eine Rinne, die Kiel und zweiten " Kiel " trennt. Nur der erste Kiel wird
von Sharpey'schen Fasern durchzogen (Abb. 6), wie es dem echten Kiel rhombischer
Schuppen entspricht. Der zweite " Kiel " ist frei von Sharpey'schen Fasern, an
seiner Hinterkante miinden Kanale des Kanalsystems aus (Taf. I, Fig. 7). Das
GroBen verhaltnis zwischen Kiel und zweitem " Kiel " verschiebt sich von den
Schuppen nahe des Schultergiirtels zu denen nahe der Caudalis. Wahrend der Kiel
der Schuppen nahe des Schultergiirtels schmal und flach ist, nimmt er zu den rhombi-
schen Schuppen vor der Caudalis hin an Breite zu und ubertrifft den zweiten " Kiel "
(Abb. 2b u. Taf. I, Fig. 8b). Der Kiel erreicht die Tiefe des zweiten " Kieles " oder
die Schuppe ist an dieser Stelle sogar dicker.
Der Vorderrand verlauft meist auffallend gerade, Dorsal- und Ventralrand fallen
schrag nach caudal ab. Der Hinterrand ist pectinat gezackt.
Das f reie Feld ( = nicht von benachbarten Schuppen iiberdeckter Teil) der Schup-
pen ist reich gegliedert. Bei den hohen Schuppen ist die Ganoindecke nur nahe dem
Hinterrand gesch lessen, besonders zum Ventralrand hin ist sie in einzelne Rippen
aufgeteilt. Die Furchen zwischen diesen Rippen konnen bis auf die Knochenbasis
hinabreichen. Zum Vorderrand hin ist die Ganoindecke in einzelne Schuppchen
aufgelost, die iiber die Schuppenoberseite aufragen, das dahinter liegende Ganoin
iiberragen und iiberdecken (Abb. la u. Taf. I., Fig. 43., 5). Die Schiippchen sind
also j linger als das dahinter liegende Ganoin. Vor allem nahe dem Vorderrand ist
das Ganoin, ganz gleich ob es sich um eine geschlossene Ganoindecke (Abb. 2a u.
Taf. I, Fig. 8a), Rippen (Abb. 3a u. Taf. I, Fig. la) oder Schiippchen (Taf. I, Fig.
2a, 3, 5, 6a) handelt, mit kraftigen Langsleistchen verziert.
Besonders auf der geschlossenen Ganoindecke fallen zahlreiche Poren auf, die in
Reihen parallel zum Ventral- bzw. Dorsalrand angeordnet sind (Abb. la, 2a). Sie
liegen im ventralen Abschnitt der hohen Schuppen in den Furchen zwischen den
Rippen; gelegentlich sind sie auBerdem parallel zum Hinterrand aufgereiht (Abb.
3a u. Taf. I, Fig. la, 3). Die Poren sind die Offnungen der Kanale, die von den
Querkanalen zwischen den groBen Kanalraumen aufsteigen (Abb. 4 u. Taf. IV,
Fig. i) . Die groBen Kanalraume sind parallel zu Ventral- bzw. Dorsalrand angeord-
net, entsprechen dem Verlauf der mit Ganoin bedeckten Rippen, unter denen die
Kanalraume liegen. In der gleichen Weise, wie die Kanalraume den Rippen folgen,
ziehen sie auch in die groBeren Schiippchen hinein, so daB unter dem vorderen
dorsalen Abschnitt des freien Feldes ein mehrschichtiges Kanalsystem entsteht. Das
Kanalsystem ist auf den mittleren Bereich der Schuppe beschrankt. Rostral warts
endet es vor dem mit Ganoin bedeckten freien Feld, wo zahlreiche Poren ausmiinden.
Caudalwarts miinden die meisten Kanale am Hinterrand des zweiten " Kieles "
aus (Taf. I, Fig. 7), nur wenige reichen in die Zacken des Hinterrandes hinein.
Abb. 2 ( = Taf. I, Fig. 8) zeigt eine Seitenlinienschuppe aus der hinteren Korper-
halfte mit deutlich sichtbarer vorderer Offnung des Seitenlinienkanals, wahrend
die hintere Offnung vom Hinterrand des zweiten " Kieles " verdeckt wird. AuBer
dieser rhombischen Seitenlinienschuppe enthielt das Material zwei schlecht erhaltene
Seitenlinienschuppen, die hoher als lang sind. Die hohen Schuppen selbst werden
nicht vom Seitenlinienkanal durchzogen. Der schrage Schlitz im oberen Abschnitt
der hohen Schuppe BM: P 48851 (= Taf. I, Fig. 2) markiert die Offnung des Grub-
PAL^ONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON
349
chenorgans (danach 1st es wahrscheinlich, daft diese Schuppe im vorderen dorsalen
Korperabschnitt lag), sie enthalt aber keinen Seitenlinienkanal. — Die Seitenlinie
verlauft entweder ventral oder dorsal der hohen Schuppen an der Flankenmitte.
HISTOLOGIE. Fiir histologische Untersuchungen ist das Schuppenmaterial sehr
ungiinstig erhalten, aber nach einigen Schliffen laBt sich die Innenstruktur abklaren
(Abb. 5, 6). Die Schuppen zeigen den typischen Aufbau einer palaeoniscoiden
Ganoidschuppe mit Knochen-, Dentin- und Ganoinschicht. Die Knochenschicht
ist durch Kiel und zweiten " Kiel " verhaltnismaBig dick. Eine Schichtung der
Knochenschicht ist zu beobachten, Knochenzellen sind ausgebildet, Williamson'sche
Kanale konnten nicht festgestellt werden. Die Sharpey'schen Fasern sind auf den
ABB. 3a, 4. Ligulalepis toombsi n.g. n. sp., Spirifer yassensis Kalk, Unterdevon, New South
Wales, Australien. 3a, BM: P 48853. " Right bank of Murrumbidgee, boulders
probably nearly in situ, on shore and up hillside, 2500 yds. due E. of Majurgong T.S. "
Hohe Schuppe aus der Region dicht hinter dem Schultergurtel, rechte Korperseite.
AuBenseite. X32. 4, BM: P 48855. " Top of spur falling west to left bank of Mur-
rumbidgee, 1800 yds. at 347° magnetic from Majurgong T.S. " Hohe Schuppe der rechten
Korperseite etwa aus der Korpermitte, dargestellt das Kanalsystem, die hoher liegenden
Kanale heller, x 60. gr^' = Hinterrand des zweiten " Kieles ".
• = Offnungen der Kanale auf der Schuppenoberseite, O = Offnungen der Kanale
auf der Schuppeninnenseite.
350
PAL^ONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON
(ersten) Kiel beschrankt natiirlich abgesehen da von, daB sie am Dorsal- und
Ventralrand der Schuppen wie in alien rhombischen Schuppen zu nnden sind.
XJber der Knochenschicht liegt das stark ausgebildete Kanalsystem. Die Dentin-
rohrchen steigen nicht direkt von den Kanalen als Auslaufer je eines Odontoblasten
nach oben auf . Vielmehr gehen von den groBen Kanalen relativ dtinne Rohrchen
ABB. 5, 6. Ligulalepis toombsi n.g. n. sp., Spirifer yassensis Kalk, Unterdevon, " left bank
of Murrumbidgee, rock face in gully 1200 yds. at 39° magnetic from Majurgong T.S. "
New South Wales, Australien. 5, BM: P 48842. Ventraler Abschnitt eines dorsal-
ventralen Vertikalschliffes, x 140. 6, BM: P 48841. Rostral-caudaler Vertikal-
schliff, x 140.
k = Kiel, k' = zweiter " Kiel ", o = Gebiet, wo die Kanale nach caudal aus der
Schuppe ausmiinden.
(aber dicker als die am Ende verastelten Dentinrohrchen) aus, die sich verzweigen
und dann parallel zu den Wachstumszonen des Dentins verlaufen. Von diesen
parallel den Wachstumszonen verlaufenden Rohrchen zweigen erst die Dentinrohr-
chen nach oben ab, die sich an den Enden verasteln. Aber auch die parallel den
Wachstumszonen verlaufenden Rohrchen verasteln sich an den Enden. Die
einzelnen Dentinbereiche sind gegeneinander durch Resorptionslinien abgegrenzt.
Etwas iiberraschend ist, daB eine Skulpturrippe nicht einem Dentinbereich entspricht,
sondern daB das Dentin der ventral nachsten Rippe auf die dorsal gelegene iiber-
greift. Die Resorptionslinie verlauft senkrecht durch eine Skulpturrippe (Abb. 5).
Das Ganoin ist diinn und wahrscheinlich einschichtig, da keine Schichtung beobachtet
werden konnte.
PALvEONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON 351
VERGLEICHE. Innerhalb der Palaeoniscoidea gibt es keinen Fisch mil hohen
Schuppen der Gestalt wie Ligulalepis. Nur im rostral-caudalen Vertikalschliff
erhalt man eine Vergleichsmoglichkeit und zwar iiberraschenderweise mit den
geometrisch rhombischen Schuppen von Cheirolepis. Schneidet man eine Chei-
rolepis-Schuppe in der Richtung der Korperlangsachse (= Diagonale der Schuppe), so
erhalt man ebenfalls einen Kiel mit Sharpey'schen Fasern und einen zweiten " Kiel ",
an dessen Hinterrand wie bei Ligulalepis das Kanalsystem ausmundet (Taf. I,
Fig. 10 u. Aldinger, H. 1937, Abb. 506, S. 197). Hier wird der zweite " Kiel "
allerdings im Gegensatz zu Ligulalepis in seinem vorderen Abschnitt von Sharpey'
schen Fasern durchsetzt, ist aber am Hinterrand vollig frei von Sharpey'schen
Fasern. Auch hier verliert die Schuppe hinter dem zweiten " Kiel " stark an
Dicke, der rostrale Abschnitt ist aber anders als bei Ligulalepis geformt. Das
Kanalsystem liegt im dorsalen Abschnitt der hohen Schuppen von Ligulalepis wie
bei Cheirolepis in verschiedenen Ebenen. Knochenzellen sind in der Knochen-
schicht beider Gattungen ausgebildet, das Fehlen Williamson'scher Kanale ist beiden
Gattungen ebenfalls gemeinsam.
Diesen Ahnlichkeiten der Schuppen von Ligulalepis und Cheirolepis im rostral-
caudalen Schnittbild stehen aber grofie Unterschiede im Hartgewebe und der
Schuppenform gegeniiber. So ist bei Cheirolepis das Ganoin mehrschichtig, bei
Ligulalepis nur einschichtig. In den Schuppen von Cheirolepis reichen die Dentin-
rohrchen zwischen die Ganoinlamellen, sie zweigen direkt von den Kanalen ab und
nicht erst von diinnen Rohrchen wie bei Ligulalepis. Nicht zu iibersehen ist der
Unterschied in der Form der Schuppen beider Palaeoniscoidea-Gattungen. So
mag das gleiche Schnittbild nur eine Zufalligkeit sein und nicht auf verwandt-
schaftliche Beziehungen hinweisen.
Das Kanalsystem von Ligulalepis zeigt im ventralen Abschnitt der hohen Schup-
pen eine Anordnung wie das Kanalsystem in A etheretmon valentiacum White (Aldinger,
H. 1937, Abb. 91, S. 305). Hier folgen weite Kanale den Skulpturrippen, von
denen kurze und viel schmalere Querkanale abzweigen. T. Cavender 1963 bezeichnet
diese Kanalanordnung als Aetheretmon-Typ (Cavender, T. 1963, Taf. V, Fig. F) und
sieht sie vertreten bei Aeth. valentiacum White, Haplolepis tuber culata (Newberry)
und einigen Rhadinichthys-Arten. Im dorsalen Abschnitt der Schuppen von
Ligulalepis findet man diese RegelmaBigkeit in der Kanalanordnung nicht.
DIALIPINA nov. gen.
DEFINITION. Gattung der Palaeoniscoidea mit annahernd gleich hohen wie
langen Schuppen an den Flanken. Ganoin nur auf den isolierten Rippen ausgebildet ;
caudalwarts enden die Rippen in Spitzen, und zwischen diesen legt sich die neue
Ganoingeneration in alternierend sitzenden Flecken an. Kraf tiger Dorn, aber flache
Grube auf der Innenseite ; Kiel nur schwach ausgebildet und vor der Verbindungslinie
Grube-Dorn liegend. AuBer Schuppen ein Knochenstiick bekannt, dessen Oberflache
nur mit Ganoinflecken verziert ist. UnregelmaBiger Verlauf der Williamson'schen
Kanale.
352 PAL^ONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON
DERIVATIO NOMINIS. SiaXei'neiv (griech.) = dazwischenstehen (bezieht sich auf
die alternierende Stellung der Ganoinflecken nahe dem Hinterrand).
Dialipina salgueiroensis gen. et sp. nov.
(Abb. 7-n, Taf. I, Fig 9 u. Taf. II)
DEFINITION. Die mit Ganoin bedeckten Rippen laufen im vorderen Teil des
freien Feldes etwa parallel dem Vorderrand, biegen dann nach caudal ab, um dann
dem Ventralrand zu folgen. Verzierung der Ganoinrippen im vorderen, dem
Vorderrand parallel verlaufenden Abschnitt mit feinen Langsleistchen, diese auch
auf den Ganoinflecken des Knochenstiickes ; der Hinterrand der Ganoinflecken nahe
dem Vorderrand des Knochenstiickes fein gezackt. Hinterrand der Schuppen
unregelmaBig serrat.
FUNDSCHICHT/-ORT. PDelorme Formation, Unterde von /Anderson River, Nord-
westkanada.
MATERIAL. 205 Schuppen und Schuppenbruchstiicke (22 isoliert, die iibrigen auf
dem Gestein), i Knochenbruchstiick, 12 Schliffe.
HOLOTYP. NMC 11608 (Abb. 7 u. Taf. II, Fig. 2).
DERIVATIO NOMINIS. salgueiroensis — zu Ehren von C. Salgueiro, dem Zeichner
aller Abbildungen dieser Arbeit.
STRATIGRAPHIE. Das von Dr. A. C. Lenz, Standard Oil, California gesammelte
Material wurde von Dr. D. Baird, Princeton, USA an Dr. T. 0rvig, Stockholm zur
Bestimmung geschickt. 1962 hat ein Student (N.-A. Morner) das Material im
Rahmen einer Examensarbeit durchgesehen, veroffentlich wurde aber bisher nur
ein gut erhaltener Dipnoer-Unterkiefer (Jarvik, E. 1967). Als Unterlage zur
genauen Bestimmung des Alters der devonischen Schichten am Anderson River
existiert keine Untersuchung der Invertebratenfauna, zitiert seien daher die Anga-
ben des National Museum of Canada:
" Outcrop locality AR.25 .58. of Mr. Ben Moore's Anderson River traverse (made in
the Summer of 1958 by boat).
Location — Latitude 68° n' North 125° 49' West — on Anderson River just upstream
from Junction with Ross River.
The strata as described by Mr. Moore are as follows, measured from the base of the
outcrop upwards stratigraphically:
50 feet Black, calcareous shales and shaly limestone, slabby to flaggy rarely
massive with abundant fish remains and possible small brachiopods with
bands of limestone, microcrystalline, blocky, medium grey coloured also
containing fish remains.
20 feet Limestone cryptocrystalline, medium dark grey coloured.
50 feet Dolomite breccia and limestone.
PAL^EONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON 353
This outcrop is separated by a covered interval from apparently underlying
strata (thickness not stated) which contains fossils identified by Dr. D. J. McLaren
as IHalysites sp. and Catenipora sp. (Locality AR. 11.58) and Favosites sp., Haly sites
sp. with Lambeioceras Iambi (Locality AR.i.58). The fish remains of AR.25-58
were considered to be " possibly Lower Devonian " by Dr. McLaren. The outcrop
is apparently overlain after a covered interval (thickness not stated), by strata which
include the brachiopod Schuchertella nevadensis identified by Dr. D. J. McLaren
(LocaUty AR.56.58).
The shales and limestones of AR . 25 . 58 have been tentatively correlated with the
Delorme Formation1. The overlying breccia is possibly correlative with the Bear
Rock Formation2. "
N.-A. Morner 1962 kam bei der Durchsicht des gesamten Fossilmaterials (Acan-
thodii, Cladoselachiidae, Palaeoniscoidea, Porolepiformes, Dipnoi, Conchostraca,
Ostracoda, Brachiopoda, Conodonta und Charophyta) zu der Auffassung, daB das
Vorkommen in das oberste Unterdevon oder unterste Mitteldevon einzustufen sei
(S. 13). Die Invertebraten sind zu schlecht erhalten, um sie zu einer Altersbestim-
mung heranziehen zu konnen. Die Pflanzen (Charophyta, von B. Lundblad,
Palaeobotaniska sektionen, Naturhistoriska Riksmuseet, Stockholm bestimmt als
" Trochiliscus sp. " und " Sycidium sp. ") lassen eine genaue Einstufung auch nicht
zu, ahnliche Funde aus Kanada sind der Onondaga Formation, oberstes Unterdevon,
zugeordnet worden (Peck, R. E. 1953, S. 212).
Es stehen sich also zwei Ansichten liber das Alter der Schichten gegeniiber
(oberstes oder unterstes Unterdevon).
MORPHOLOGIE. Das besonders Auffallige der Schuppen von Dialipina ist der
alternierende Zuwachs der mit Ganoin bedeckten Flecken am Hinterrand der Schuppe.
Im vorderen Teil des freien Feldes laufen die Ganoinrippen etwa parallel zum
Vorderrand, biegen dann nach caudal um und setzen dann etwa parallel zum Ventral-
rand fort. Diese Rippen werden caudalwarts nicht mehr verlangert, sondern
Dentin -J- Ganoin werden in Flecken zwischen ihnen angelegt. Auch die weiter
folgenden Flecken werden alternierend zu den vorher angelegten angeordnet. Man
kann einzelne Zuwachszonen der Flecken verfolgen, die der Abfolge der Rippen
nahe dem Ventralrand entsprechen (2, 3, 4 in Abb. 70). Der Zuwachs der Flecken
verlagert sich zum oberen hinteren Schuppenabschnitt. In den symmetrischen
Schuppen erfolgt dagegen der Zuwachs immer symmetrisch zur Langsachse der
Schuppe.
Feine Langsleistchen, die etwa parallel zum Ventralrand verlaufen, verzieren die
Rippen besonders im vorderen zum Vorderrand parallel verlaufenden Abschnitt.
Die Rippen steigen im vorderen, zum Vorderrand parallel verlaufenden Abschnitt
langsam nach caudal an, um dann steil abzuf alien. Diese Steilkante zieht hinter
dem Umbiegen der Rippen in caudale Richtung auf die Mitte der Rippen und auf
die Spitze am Ende zu. Manchmal zeigen auch die Flecken eine derartige Kante in
der Mitte.
1 oberstes Silur bis unterstes Unterdevon.
2 Mitteldevon.
354
PAL/EONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON
Die Schuppen an den Korperflanken sind etwa gleich hoch wie lang (Abb. 7,
Taf. I, Fig. 9 u. Taf. II, Fig. 2), werden langgestreckter zur Ventralregion und zur
Caudalis hin (Taf. II, Fig. 3). Der Vorderrand ist gerade und schrag nach caudal
geneigt. Die vordere obere Ecke ist lang ausgezogen, ohne vom Dorsal- oder
Vorderrand winkelig abgesetzt zu sein. Die vordere untere Ecke ist abgerundet,
der gerade Vorderrand geht allmahlich in den nach ventral ausschwingenden Ventral-
rand iiber. Der Hinterrand ist unregelmaBig serrat gezackt. Ein kraf tiger Dorn
sitzt dem Dorsalrand auf, er verliert von seiner Basis bis zur Spitze nur wenig von
seiner Breite und endet breit abgerundet. Dem kraftigen Dorn entspricht auf der
Innenseite eine ebenso breite, aber relativ flache Grube. Die gesamte Schuppe ist
iiberhaupt im Verhaltnis zu ihrer GroBe recht diinn. Der Kiel tritt nur schwach
hervor, er verlauft vor der Verbindungslinie Grube-Dorn.
Relativ haufig sind in dem Material symmetrisch oder nahezu symmetrisch
gebaute Schuppen (20 = 10 % aller Schuppen) . Bei den symmetrischen Schuppen
(n) handelt es sich um die Schuppen der dorsalen und der ventralen Mittellinie, die
etwas asymmetrischen Schuppen (9) liegen vor den Ansatzstellen der Flossen und
vor der Analofmung (Taf. II, Fig. i).
ABB. 7. Dialipina salgueiroensis n.g. n. sp., NMC 11608, Holotyp, Unterdevon, PDelorme
Formation, Anderson River, gerade stromaufwarts des Zusammenflusses mit dem Ross
River (68° n' Nord/i25° 49' West), Nordwestkanada. Schuppe aus der vorderen
Korperhalfte der linken Korperseite. a, AuBenseite, x 32. b, Innenseite, x 16. c,
Schema der Wachstumsabfolge, 1-4 = Zuwachszonen am Hinterrand, x 16.
PAL.EONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON
355
Fig. 4 (Taf. II) zeigt ein Knochenstiick, das nur eine natiirliche Begrenzung
besitzt — die schwach S-formig gebogene Vorderkante. Alle iibrigen Begrenzungen
sind Bruchkanten. Die Orientierung erfolgte auf Grund der Langserstreckung der
groBeren Flecken (im hinteren Teil), die auch reich mit feinen Langsleistchen
verziert sind. Die Flecken sind nur im hinteren Teil groBer und flacher, im vorderen
sind sie auf die ganze Erstreckung parallel zum Vorderrand klein und nach caudal
steil aufgerichtet. Der Hinterrand dieser vorderen Schiippchen ist fein gezackt.
Auf der Innenseite des Knochenstiickes verlauft ein Wulst von der Mitte des dorsalen
Teiles nach ventral an den Vorderrand. Wahrscheinlich ist dies Knochenstiick ein
Teil des Schultergurtels (PCleithrum). Es zeigt, daB die Kopfknochen von Dialipina
mit einzelnen Ganoinflecken verziert sind.
Das Kanalsystem (Abb. u) folgt der mit Ganoin bedeckten Skulptur. Weite
Kanale folgen den Rippen vom Anfang bis nahe an die Spitze am Ende, kurz vor der
Spitze verdickt sich der Kanal. Von diesen Hauptkanalen zweigen etwa recht-
winklig schmalere Querkanale ab, die zum Teil nur iiber den Rand der Rippe hinaus-
ragen und dort ausmiinden. Einige der Querkanale stellen die Verbindung zum
Hauptkanal der benachbarten Rippe her. Etwas unregelmaBiger scheint das
0,1mm
O,l 'mm
ABB. 8-10. Dialipina, salgueiroensis n.g. n. sp., Unterdevon, PDelorme Formation, Ander-
son River, gerade stromauf warts des Zusammenflusses mit dem Ross River (68° u'
Nord/i25° 49' West), Nordwestkanada. 8, NMC 11607. Rostral-caudaler Vertikal-
schliff, X75- ga, NMC 11606. Dorsal-ventraler Vertikalschliff, x 75. gb, Ausschnitt
aus Abb. ga, um die Williamson'schen Kanale zu zeigen, x 300. A. 10, NMC 11605.
Dorsal-ventraler Vertikalschliff durch den Kiel. X 75.
356 PAL^ONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON
Kanalsystem in der Nahe der Flecken zu sein. In den Flecken selbst sieht man den
Hauptkanal sich verdicken wie in den Spitzen der Rippen.
HISTOLOGIE. Die Schuppen bestehen zum groBten Teil aus der Knochenschicht.
Ganoin- und Dentinschicht sind im Verhaltnis dazu recht diinn. Der diinne Ganoin-
belag zeigt keine Schichtung, oft erkennt man die Ganoinschicht erst in polarisiertem
Licht (Taf. IV, Fig. 6, 7). Die Dentinrohrchen sind regelmaBig unter der gesamten
Ganoinschicht ausgebildet, sie gehen von den Kanalen bzw. dem Niveau des
Kanalsystems aus (deutlicher Farbunterschied gegeniiber der Knochenbasis).
Unter dem Kanalsystem wurden keine Dentinrohrchen beobachtet. Die Kanale
sind in den meisten Schuppen recht flach, was zumindest zum Teil auf Einwirkung
bei der Fossilisation (Setzung des schiefrigen Gesteins) zuruckzufuhren ist. Nur
gelegentlich findet man Schuppen im Gestein, die hohere Kanale zeigen (Taf. IV,
Fig. 7). Die Knochenbasis ist geschichtet, es fehlen Knochenzellen, dafiir sind
Williamson 'sche Kanale sehr zahlreich (Abb. 8, 9). Die Williamson'schen Kanale
haben einen unregelmaBigen Verlauf, sie wechseln in ihrem Verlauf sehr in ihrer
Dicke, verzweigen sich und senden gelegentlich kurze Fortsatze ab, zahlreicher
gegen das Ende zu (Abb. gb). Sie stehen nicht in Verbindung mit dem Kanal-
system oder den Dentinrohrchen. Einen gestreckteren Verlauf zeigen die William-
son'schen Kanale, die von oben (auBen) in die Knochenbasis einstrahlen und sich
nur am Ende verzweigen (Abb. 10). Ihr Verlauf entspricht dem der Williamson'-
schen Kanale in alien rhombischen Ganoidschuppen.
VERGLEICHE. Einzelne Skulpturrippen, die wie bei Dialipina isoliert auf der
Knochenbasis sitzen, zeigen die Schuppen von Aether etmon whitei Moy-Thomas
(Moy-Thomas, J. A. 1938, Abb. 6, S. 315) und teilweise Orvikuina (Abb. I3a). Beiden
Formen fehlt aber die alternierende Anlage der Flecken nahe dem Hinterrand, der
Hinterrand der Schuppen von Aeth. whitei ist gerade. Eine auffallige tJbereinstim-
mung im Verlauf der Skulpturrippen im vorderen Teil des freien Feldes zeigt
StrepheoschemafouldenensisWhite (White, E. 1927, Abb. 45, S. 283) — soauch vieleRha-
dinichihys-Aiien — die f einen Langsleistchen sind ebenfalls vorhanden. Aber auch
hier ist keine Andeutung einer alternierenden Anlage von Flecken am Hinterrand zu
finden, vielmehr wird im Gegenteil der hintere Teil des freien Feldes von einer
geschlossenen Ganoinflache bedeckt.
Der histologische Bau der Schuppen von Dialipina zeigt in der auffalligsten
Struktur, den unregelmaBigen Williamson'schen Kanalen, Ahnlichkeit mit Orvikuina
vardiaensis Gross (Gross, W. 1953, Abb. 9, 12, 13), auch fehlen bei beiden Formen
die Knochenzellen. Der Aufbau des Kanalsystems aus Langskanalen, von denen
Querkanale abzweigen, ist bei beiden Formen der gleiche. Man kann das Kanal-
system von Dialipina ebenfalls dem Aetheretmon-Typ (siehe S. 351) zuordnen, nur
ist der Unterschied im Lumen zwischen Langs- und Querkanalen nicht so groB wie
bei Aether etmon. Orvikuina und Dialipina unterscheiden sich in der Ausbildung
des Dentins, vor allem treten bei Dialipina unter dem Kanalsystem keine Dentin-
rohrchen auf, in der Anlage der Skulpturrippen und in der Schuppenform. Mit dem
t)berlagern der Skulpturrippen ist bei Orvikuina ebenfalls ein mehrschichtiges
Kanalsystem verbunden, beides fehlt den Schuppen von Dialipina. DaB Orvikuina
vor allem langgestreckte Schuppen gegeniiber den mehr quadratischen von Dialipina
PAL^ONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON
357
besitzt, mag kein schwerwiegender Unterschied sein, aber das Fehlen einer Dorn-
Grube-Gelenkung bei Orvikuina steht doch in starkem Gegensatz zu der Ausbildung
eines kraftigen Domes bei Dialipina. Trotzdem scheint Orvikuina auf Grund des
histologischen Baues die Gattung innerhalb der Palaeoniscoidea zu sein, die Dialipina
am nachsten steht.
0,1mm
ABB. ii. Dialipina salgueiroensis n.g. n. sp., NMC 11611, Unterdevon, PDelorme Forma-
tion, Anderson River, gerade stromaufwarts des Zusammenflusses mit dem Ross River
(68° n' Nord/i25° 49' West), Nordwestkanada. Schuppe der rechten Korperseite,
vermutlich aus der Korpermitte (= Taf. II, Fig. 3), dargestellt das Kanalsystem.
X40.
• = Offnungen der Kanale auf der Schuppenoberseite, O = Offnungen der Kanale
auf der Schuppeninnenseite.
Orvikuina sp.
(Abb. 12-19, Taf. Ill u. Taf. IV, Fig. 4)
FUNDSCHICHT/-ORT. Grey Hoek Schichten, unteres Mitteldevon/Westteil der
Nordseite von V-Vaerdalen, Wood Bay, Spitzbergen.
MATERIAL. 573 Schuppen und Schuppenbruchstiicke, 13 Bruchstucke von
Deckknochen des Kopfes und 28 Schliffe (davon 18 aus der Schliffsammlung W.
Gross, Berlin: Nr. 2571-2588).
STRATIGRAPHIE. Das Alter der Grey Hoek Schichten ist unsicher. Friend, F.
1961 und Winsnes, Th.S., Heintz, A. u. Heintz, N. 1966 (S. 21, 23) halten sowohl ein
Alter von oberem Unterdevon als auch ein Alter von unterem Mitteldevon fur
moglich. Die bisher publizierte Fischfauna laBt eine genaue Einstufung nicht zu,
die hier beschreibenen Palaeoniscoidea- Reste lassen einen Vergleich mit dem Balti-
kum zu, wo Orvikuina-Schuppen in der Luga-Stufe (Mitteldevon) auftreten. Eben-
GEOL. 1 6, 7.
33
358 PAL^ONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON
falls fiir Mitteldevon sprechen die Pflanzenreste, allerdings sind beide Arten (Arcto-
phyton gracile Schweitzer und Psilodendrion spinulosum H0eg) endemisch, nur aus den
Grey Hoek Schichten bekannt. Auf Grund der Organisationshohe der Pflanzen,
vor allem von Arctophyton gracile Schweitzer, halt H. J. Schweitzer ein unterdevoni-
sches Alter fiir ausgeschlossen, er stuft die Grey Hoek Schichten ins untere Mittel-
devon (mittleres Eifelium) ein.
MORPHOLOGIE. Die Gattung Orvikuina wurde von W. Gross 1953 anhand eines
kleinen Materials (20 Schuppen) aus dem Mittel Old Red des Baltikums aufgestellt.
Ihm lagen nur langgestreckte Schuppen vor, diese Schuppen bilden auch den Haupt-
teil an dem Material aus Vaerdalen (453 Schuppen und Bruchstiicke von Schuppen
der Gestalt wie auf Abb. 14, 15 u. Taf. Ill, Fig. 2-6 dargestellt =79% aller
Schuppen). Mehr rhombische Schuppen sind seltener, Schuppen eines Aussehens
wie auf Abb. 12 (= Taf. Ill, Fig. i) 40 Exemplare (=7%) und Schuppen mit
isolierten, stark verzierten Rippen (Abb. 13 u. Taf. Ill, 7, 8) 77 Exemplare (= 13,5 %).
Wohl mag fiir das Vorherrschen der langgestreckten Schuppen sowohl im Baltikum
als auch in Spitzbergen zum Teil selektive Ablagerung verantwortlich sein, aber da
in Spitzbergen zusammen mit den langgestreckten Schuppen ebenfalls rhombische
auftreten, ist anzunehmen, dafi es sich bei Orvikuina um eine Palaeoniscoidea-Form
mit vorwiegend langgestreckten Schuppen handelt. Die fiir die Ventralregion
charakteristischen Schuppen miissen weit auf die Flanken hinaufreichen. Sym-
metrische Schuppen der ventralen oder der dorsalen Mittellinie sind aufierst selten
(3 Exemplare =0,5%).
Ein Merkmal der Orvikuina-Sctmppen, das auch W. Gross 1953 hervorhebt (S.
101), ist das Fehlen einer Grube-Dorn-Gelenkung. Diese Gelenkung fehlt oft bei
rhombischen Ganoidschuppen aus der Ventralregion. Bei Orvikuina ist aber auch
an den rhombischen Schuppen der Flanken diese Gelenkung nicht vorhanden. Man
sieht nur im hinteren Abschnitt des Dorsalrandes der rhombischen Schuppen (Abb.
13 u. Taf. Ill, Fig. 7, 8) eine Ausbuchtung nach dorsal, der eine seichte Vertiefung
nahe dem Ventralrand auf der Innenseite entspricht. Eine Andeutung dieser
Ausbuchtung am Dorsalrand zeigt in W. Gross 1953 die Abb. 8B (Taf. 6, Fig. n).
Auch ohne Dorn-Grube-Gelenkung iiberlagern sich die Schuppen stark, am Dorsal-
rand liegt ein breiter Knochensaum (" glatter Saum " bei W. Gross 1953, S. 101),
der am Ventralrand der Innenseite in eine entsprechende Vertiefung hineingreift.
Ein Kiel ist auf der Schuppeninnenseite trotz Fehlens der Dorn-Grube-Gelenkung
ausgebildet, er tritt sogar manchmal bei den langgestreckten Schuppen schmal und
stark hervor (Taf. Ill, Fig. 2b bzw. Gross, W. 1953, Abb. 8K).
Die vordere obere Ecke ist ausgezogen, ohne vom Vorder- oder Dorsalrand abge-
setzt zu sein. Der Vorderrand ist gerade und nach caudal geneigt, manchmal ist er
in einen oberen und einen unteren Abschnitt iiber eine schwache Ecke dazwischen geteilt
(Abb. 12). Der Ventralrand verlauft gerade oder schwingt etwas nach ventral aus.
Der Hinterrand endet meist in einer Spitze, seltener in zwei (31 Exemplare wie auf
Abb. 12) oder sogar in drei (9 Exemplare), abgesehen natiirlich von Schuppen des
Aussehens wie Abb. 13.
Das freie Feld der langgestreckten Schuppen ist von einer einheitlichen Ganoin-
flache bedeckt, die sich zum Vorderrand hin in einzelne Zungen auflb'st. Die
PAL^ONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON
359
Schuppen mit 2 oder 3 Zacken am Hinterrand besitzen ebenso viele durch tiefe
Furchen voneinander getrennte Ganoinflachen, diese losen sich ebenfalls nach
vorne hin in Zungen auf und gelegentlich sind ihnen einzelne Flecken vorgelagert
(Abb. i2a = Taf. Ill, Fig. i), was auch bei manchen langgestreckten Schuppen zu
beobachten ist (Abb. 15). Alle diese einheitlichen Ganoinflachen bauen sich aus
zahlreichen Streifen auf, die sich jeweils dorsal und ventral an die Ganoinflache an-
lagern — besonders deutlich in Abb. 15 (= Taf. Ill, Fig. 3) — und nach vorne in die
einzelnen Zungen fortsetzen. An das Zentralfeld (i in Abb. i5b) legt sich zuerst
15 a
ABB. i2-i5a. Orvikuina sp., Grey Hoek Schichten, unteres Mitteldevon, Westteil der
Nordseite von V-Vaerdalen, Wood Bay, Spitzbergen. 12, Sto: P 6403. Schuppe der
linken Korperseite vermutlich von der Korperflanke, Schuppe mit zwei flachen Ganoin-
riicken. a, AuBenseite. b. Innenseite. x 32. 13. Sto: P 6408. Schuppe der rechten
Korperseite aus der vorderen Korperhalfte, mit schmalen, stark verzierten Skulpturrip-
pen. a, AuBenseite. b, Innenseite. x 32. 14, Sto: P 6401. Schuppe der rechten
Korperseite aus der Ventralregion, fast geschlossene Ganoindecke. a, AuBenseite. b,
Innenseite. x 32. I5a, Sto: P 6400. Schuppe der linken Korperseite aus der Ventral-
region, fast geschlossene Ganoindecke, die die Wachstumsabfolge deutlich zeigt. AuBen-
seite. x 32.
GEOL. 16, 7. 33§
360 PALvEONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON
ventral ein Streifen an, der nachste folgt dorsal, dann wieder ventral und so welter
(Wachstumsabfolge 1-6 in Abb. I5b). Da man meist auf den Schuppen die einander
entsprechenden ventralen und dorsalen Streifen vorfindet und da diese im caudalen
Abschnitt der Schuppe, wo sie aneinander stoBen, eng aneinander liegen, ist zu
folgern, daft beide Streifen in einer kurzen Zeitspanne nacheinander abgelagert
werden (Gross, W. 1953, S. 105: " Zweizahl "). Abb. 16 zeigt diese Wachstumsab-
folge im Schnitt. Auf das Ganoin des Zentralfeldes (i in Abb. I5b) bzw. des vorher
abgelagerten Streifens legt sich seitlich das Ganoin des nachsten Streifens. Das
Dentin grenzt ohne Resorptionslinien aneinander. Die Ganoinflache wird aber
nicht nur nach dorsal und ventral sondern auch nach rostral vergroBert, und von
rostral greifen die Streifen dann auf die ganze Ganoinflache iiber (Abb. 18), so daB
man das fiir Orvikuina typische Schnittbild mit iibereinander liegenden Rippen
erhalt (Abb. 19).
Das Ganoin ist mit feinen Langsleistchen verziert. Diese treten besonders
deutlich nahe dem Vorderrand hervor, sind aber auch am Ventral- und Dorsalrand
der Ganoinstreifen ausgebildet (Abb. I2a, 143.) und heben innerhalb einer ge-
schlossenen Ganoinflache die Begrenzung der einzelnen Streifen hervor (Abb. I2a,
I5a) . Diese Skulptur der Langsleistchen tritt sehr kraf tig auf den isolierten Rippen
rhombischer Schuppen (Abb. i3a, Taf. Ill, Fig. ya, 8) hervor. Diese rhombischen
Schuppen zeigen die gleiche Wachstumsabfolge. Zuerst wird eine kurze Rippe im
Zentrum angelegt, um die sich ventral und dorsal die nachsten Rippen allerdings
getrennt von den vorhergehenden legen. Auch hier greifen spater von rostral her
Rippen iiber die friiher angelegten hinweg (Taf. Ill, Fig. 9), so daB man das gleiche
Schnittbild wie Abb. 19 erhalt. Da alle Schuppen isoliert gefunden worden sind,
ist es nicht ganz sicher, daB die rhombischen Schuppen mit den stark verzierten
Rippen demselben Fisch angehoren wie die langgestreckten Schuppen. Der histo-
logisch gleiche Aufbau und die gleiche Schuppenform (Fehlen eines Domes) sprechen
aber sehr dafiir, daB es sich hier um die starker skulptierten Schuppen der vorderen
Korperhalfte handelt. Und so ist anzunehmen, daB die Kopfknochen von Orvi-
kuina sp. ebenfalls mit derartig stark skulptierten Rippen verziert sind. Fragmente,
die Kopfknochen zuzuordnen sind, zeigen diese Skulptur, ebenso ein Fragment (PMO :
A 34000) aus dem siidlichen Teil Spitzbergens (R0ykensata, Stormbukta, Sorkapp
Land: ebenfalls Grey Hoek Schichten).
Das Kanalsystem ist von Gross, W. 1953 (Abb. n) im Ausschnitt dargestellt
worden. Hier soil nur noch an einer Schuppe mit zwei Ganoinflachen der Zusam-
menhang zwischen zonarem Wachstum und Kanalsystem gezeigt werden (Abb. 17).
Unter den beiden zentralen Ganoinflachen verlauft ein Langskanal, von dem zahl-
reiche Querkanale abgehen und auBerhalb der Ganoiniiberdeckung ausmiinden.
Jedem neuen Streifen, der sich ventral oder dorsal an die zentrale Ganoinflache
anlagert, folgt ebenfalls ein Langskanal, der durch Querkanale mit dem ersten
Langskanal verbunden ist. Auf der Innenseite offnen sich bei einigen Schuppen
sehr groBe Poren der absteigenden Kanale (Abb. I2b = Taf. Ill, Fig. ib).
HISTOLOGIE. Der histologische Aufbau der Schuppen (Abb. 16, 18, 19 u. Taf. IV,
Fig. 4) stimmt mit dem von Orvikuina vardiaensis Gross (Gross, W. 1953, Abb.
gA, B) iiberein. Die Ausbildung von Ganoin- und Dentinschicht ist identisch.
PAL^EONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON 361
Gelegentlich sieht man eine Schichtung im Ganoin. Das Ganoin der einzelnen
Wachstumszonen iiberlagert sich randlich, ist stellenweise resorbiert besonders dort,
wo es weit von Dentin iiberlagert wird (Abb. 19 Mitte). Die Dentinrohrchen gehen
in alle Richtungen von den Kanalen ab und verzweigen sich nach dorsal gegen das
Ganoin hin stark. Der Verlauf der Dentinrohrchen, die nach ventral gerichtet
sind, ist unregelmaBiger. Im Bereich ventral der Kanale sind keine Konturlinien zu
17
ABB. i5b, 16, 17. Orvikuina sp., Grey Hoek Schichten, unteres Mitteldevon, Westteil der
Nordseite von V-Vaerdalen, Wood Bay, Spitzbergen. i5b, Sto: P 6400. Schuppe der
linken Korperseite aus der Ventralregion, Schema der Wachstumsabfolge (1-6). X 32.
16, Gr.B. : 2579. Dorsal-ventraler Vertikalschliff mit Wachstumsabfolge 1-5. x 100.
17, Gr.B.: 2587. Horizontalschliff durch eine Schuppe der rechten Korperseite.
Schuppe mit zwei flachen Ganoinriicken, dargestellt das Kanalsystem. x 60.
• = Offnungen der Kanale auf der Schuppenoberseite, O = Offnungen der Kanale
auf der Schuppeninnenseite.
beobachten wie im Dentin dorsal der Kanale. Der ganze Bereich, der von Dentin-
rohrchen durchzogen wird, ist dunkelbraun gefarbt (Taf. IV, Fig. 4). Der Knochen-
schicht fehlen wie bei Orv. vardiaensis die Lakunen der Knochenzellen. Wegen der
schlechten histologischen Erhaltung (haufig Umkristallisation) sind die William-
son'schen Kanale meist nicht gut oder uberhaupt nicht zu sehen. Der Langs-
schliff (Abb. 18) zeigt Williamson'sche Kanale, die von oben (aufien) in die Knochen-
schicht eindringen. Sie verlaufen gerade und verzweigen sich nur am Ende, sie
sind also wie die Williamson'schen Kanale in alien rhombischen Ganoidschuppen
362
PAL^ONISCOIDEA-SCHUPPEN AU5 DEM UNTERDEVON
ventral
ABB. 18, 19. Orvikuina sp., Grey Hoek Schichten, unteres Mitteldevon, Westteil der
Nordseite von V-Vaerdalen, Wood Bay, Spitzbergen. 18, Sto: S 2135. Rostral-caudaler
Vertikalschliff. x 70. 19, Sto: S. 2137. Dorsal-ventraler Vertikalschliff. x 90.
geformt. Williamson'sche Kanale, die von der Innenseite aufsteigen und unregel-
maBig verlauf en, kann man nur in zwei Schliffen sehen (GrB : 2575 u. 2580) . Aber auch
hier ist die Erhaltung so schlecht, daB der genaue Verlauf nicht verfolgt werden
kann. Der Unterschied zu den Sharpey'schen Fasern ist nur gering, sodaB man
nicht feststellen kann, ob sie in den Bereich dieser tibergehen oder nicht.
VERGLEICHE. Die hier beschriebenen Schuppen aus Spitzbergen stimmen in
Form und Histologie sehr mit Orv. vardiaensis Gross aus dem Baltikum iiberein.
Beide Formen besitzen langgestreckte Schuppen ohne Dorn, mit scheinbar ein-
heitlicher Ganoinoberflache und Langsleistchen an den Randern des Ganoins. Die
Anordnung und der Verlauf der Kanale und der histologische Bau der Schuppen
beider Fundpunkte stimmen vollig iiberein. DaB die Williamson'schen Kanale
im Material aus Spitzbergen selten zu sehen sind, liegt wohl nur an der schlechten
histologischen Erhaltung dieses Materials.
Die Schuppen von Orv. vardiaensis unterscheiden sich nur dadurch von Orvikuina
sp., daB die Ganoinoberflache von caudal her starker gegliedert und der Hinterrand
melirfach gezackt ist. Dieser Unterschied ist aber zu gering, urn darauf eine neue
Art zu begrunden. Andererseits konnen die rhombischen Schuppen nicht zu einer
Artdefinition herangezogen werden, da sie aus dem Baltikum nicht bekannt sind.
• W. Gross 1953 (S. 109) vergleicht Orvikuina mit Stegotrachelus . Ein histologischer
Vergleich beider Gattungen ist kaum moglich, da die Schuppen von Stegotrachelus
finlayi Woodward u. White schwarz gefarbt sind und beim Schleifen nicht durch-
sichtig werden. Morphologisch unterscheiden sich die Schuppen beider Gattungen
betrachtlich. So sind die Schuppen von Stegotr. finlayi an den Flanken hoher als
lang, langgestreckte Schuppen sind wenig vertreten, auch ist im Gegensatz zu
Orvikuina eine Grube-Dorn-Gelenkung ausgebildet. Die Ganoinoberflache ist
PAUEONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON 363
meist geschlossen und an den Randern mil sehr kraftigen Langsleistchen versehen,
die weit auf die Ganoinoberflache hinaufgreifen. Auffallend sind die groBen Poren
in der Ganoinoberflache. In alien diesen Merkmalen gleichen die Schuppen von
Stegotr. finlayi sehr den Schuppen von Moythomasia nitida Gross (Jessen, H. 1968,
Abb. 46).
Da Orvikuina die Dorn-Grube-Gelenkung fehlt, ist es nicht moglich, die Schuppen
morphologisch mil Schuppen anderer Palaeoniscoidea zu vergleichen. Auf Grand
des histologischen Baues steht Orvikuina Dialipina am nachsten (ausfiihrlicher
Vergleich siehe S. 356/357).
III. DISKUSSION ZUR HISTOLOGIE
Die Schuppen von Ligulalepis, Dialipina und Orvikuina besitzen ein gemeinsames
Merkmal, bei alien ist das Dentin nur von einer diinnen Ganoinschicht iiberdeckt,
besonders bei den unterdevonischen Gattungen Ligulalepis und Dialipina. Nahezu
alle Palaeoniscoidea legen mehrere Ganoinschichten iibereinander an (Cheirolepis
im Mitteldevon bereits viele), nur bei einzelnen ist die Ganoinschicht dunn und
einschichtig — auBer den hier beschriebenen bei Moythomasia laevigata Gross (Gross,
W. 1953, S. 100, Mitteldevon) und IGonatodus brainerdi (Thomas) (Cavender, T.
1963, Taf. II, Fig. A, unteres Mississippian) . Die diinne Ganoinschicht scheint ein
urspriinglicher Charakter der palaeoniscoiden Ganoidschuppe zu sein.
Die Schuppen von Dialipina und Orvikuina besitzen keine Lakunen fur Knochen-
zellen und bei beiden Gattungen treten unregelmaBige Williamson'sche Kanale
auf. Diese Ausbildung der Williamson 'schen Kanale wurde von T. 0rvig 19576
phylogenetisch ausgedeutet. Er sieht in den Abzweigungen der Williamson'schen
Kanale die Fortsatze von Knochenzellen, die sich nach einem ersten phylogene-
tischen Stadium der Konzentration um die Williamson'schen Kanale in diese
zuriickgezogen haben sollen (0rvig, T. 19576, S. 487). Eine Konzentration von
Knochenzellen um Kanale ist vom rezenten Polypterus (Taf. IV, Fig. 2) und von
drei triassischen Formen Perleidus stochiensis Stensio (Stensio, E. 1933, Taf. 39),
Scanilepis dubia (Woodward) (0rvig, T. 19576, Abb. 2) und Heterolepidotus sp.
(Schultze, H.-P. 1966, Abb. 47) bekannt. Nur bei Perl, stochiensis und Heterolepi-
dotus sp. sind Knochenzellen zahlreich in der Nahe echter Williamson'scher Kanale
angeordnet. Bei Scan, dubia und Polypterus erfolgt die Konzentration der Knochen-
zellen um weite Kanale, deren Lumen ein mehrfaches einer Knochenzelle betragt.
Diese Kanale munden gelegentlich an der Oberflache der Schuppe aus (Aldinger, H.
1937, Abb. 58), hierin entsprechen sie den " einfachen, weiten Kanalen " (Schultze,
H.-P. 1966, Abb. 49) der lepidosteoiden Ganoidschuppe und wohl auch den Kanalen
bei Callichthys (0rvig, T. I957b, Abb. 46) und stehen in groBem Gegensatz zu den
Williamson'schen Kanalen, die nie die ganze Schuppe durchqueren. Bei den
Kanalen von Scanilepis und Polypterus handelt es sich um aufsteigende Kanale
des Kanalsystems des Dentins und nicht um Williamson'sche Kanale der Definition
von T. 0rvig 1951, S. 365. So kann man die Konzentration der Knochenzellen bei
Polypterus und Scanilepis wohl mit dem Zustand bei Callichthys vergleichen nicht
aber mit den Williamson'schen Kanalen bei den devonischen Gattungen ; vielleicht
364 PAL^ONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON
laBt sich auch eine Entwicklung von einem Zustand ahnlich wie bei Polypterus und
Scanilepis zu einem Zustand wie bei Callichthys begriinden.
Die weiten Kanale bei Scanilepis und Polypterus zeigen noch einige Gemeinsam-
keiten, die echten Williamson'schen Kanalen fehlen. In dem Bereich, wo der Kanal
von Knochenzellen umgeben wird, trennt ihn von den Knochenzellen ein Bereich
konzentrischer Lamellen mit einer feinen radialen Streifung (Taf. IV, Fig. 3).
Dieser Bereich wird nahe der Dentinschicht von vielen unregelmaBigen Kanalchen
durchzogen (vermutlich Dentinrohrchen, siehe 0rvig, T. 19576, Fig. i) ; ahnliche,
aber noch unregelmaBigere Kanalchen gehen sowohl bei Scanilepis als auch Poly-
pterus (Sewertzoff, A. N. 1932, Taf. 7, Fig. 10) von den weiten Kanalen aus, die
annahernd horizontal am Schuppenrand ausmiinden. Die Schuppen von Scanilepis
und Polypterus zeigen also im histologischen Bau groBe Ahnlichkeiten was H. Al-
dinger 1937 (S. 227/228) bereits hervorhob.
Im Gegensatz zu den Kanalen bei Polypterus und Scanilepis entsprechen die
Kanale in den Schuppen von Dialipina und Orvikuina ganz der Definition nicht-
vascularer Williamson'scher Kanale (0rvig, T. 1951, S. 365). Ihr Lumen ist viel
geringer als das einer Knochenzelle, was bereits W. Gross 1953 betont (S. 104 oben).
Sie sind daher wohl auch wie alle nichtvascularen Williamson'sche Kanale im Sinne
0rvig's als die Auslaufer einer sich odontoblastenahnlich zuriickziehenden Knochen-
zelle zu deuten. Ihr wechselndes Lumen (An- und Abschwellen) findet sich auch
bei Williamson'schen Kanalen anderer Schuppen (Schultze, H.-P. 1966, Abb. 55b),
nur verzweigt sich der Fortsatz der basal der Schuppe sitzenden Zelle bei diesen
beiden devonischen Gattungen viel starker als gewohnlich. Diese Abzweigungen
sind aber nicht als Fortsatze mehrerer Knochenzellen zu deuten, die in den William-
son'schen Kanalen sitzen, da das Lumen der Kanale zu eng fur Knochenzellen ist.
Den weiten Kanalen in den Schuppen von Scanilepis und Polypterus, um die sich
Knochenzellen konzentrieren, entsprechen in den Schuppen von Dialipina und
Orvikuina (Abb. 16, 18 u. Gross, W. 1953, Abb. 96) die Kanale, die vom Kanal-
system zur Schuppenbasis absteigen und in deren Nahe sich wie in der gesamten
Knochenschicht keine Knochenzellen nnden.
So ist T. 0rvig 19576 (S. 487) wohl beizupflichten, daB Knochengewebe ohne
Knochenzellen bei den Actinopterygiern zumindest zweimal unabhangig voneinan-
der bei den Palaeoniscoidea und den Teleostei auftritt. Aber ein Sichzuriickziehen
der Knochenzellen in irgendwelche Kanale wahrend der Phylogenie ist abzulehnen.1
Mit der Bildung des Knochengewebes miissen immer Knochenzellen in Verbindung
stehen. DaB die Lakunen nicht in der Knochenschicht erhalten bleiben, kann
zweierlei Ursachen haben: entweder werden die Lakunen wahrend der Bildung der
Knochenschicht wieder ausgefiillt (Moss, M. L. 1961) oder sie werden wahrend des
1 J. D. Currey 1961 vergleicht die Kanaldichte in der Knochenbasis von Scanilepis (etwa 37 Kanale
pro mm.2) und Orvikuina (etwa 2300 Kanale pro mm.2) und die Kanale selbst (Scanilepis mit vascularen
und Orvikuina mit nichtvascularen Kanalen). Er kommt zu der gleichen SchluBfolgerung, d.h. er
lehnt ebenfalls eine Entwicklung azellularen Knochens in Sinne 0rvig's ab: "Though Orvikuina is seen,
therefore, to be highly specialized, it shows a different kind of specialization from that shown by Scanilepis,
and it has not simply travelled further along the line of specialization started by Scanilepis " (Currey
1961, S. 190).
Nach Einreichung des Manuskripts zum Druck machte mich Prof. Dr. W. Gross freundlicherweise
noch auf diese Arbeit aufmerksam.
PAL/EONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON 365
ganzen Bildungsprozesses nicht eingeschlossen, bleiben immer am Rand der Knochen-
schicht liegen. So sind auch in den Schuppen von Polypterus, Scan, dubia, Perl.
stochiensis und Heterolepidotus sp. die Knochenzellen im iibrigen mehr oder weniger
gleichmaBig auf die gesamte Knochenschicht verteilt.
IV. STRATIGRAPHIE UND FAUNA
Die Sedimente der drei Lokalitaten, wo die hier beschriebenen Palaeoniscoidea
vorkommen, entstammen marinem Milieu; zusammen mit den Vertebratenresten
treten Invertebraten und Conodonten auf. Die Vertebratenfauna mit Ligulalepis
vom Murrumbidgee River (Australien) ist mit Korallen, Trilobiten, Brachiopoden,
Gastropoden, Scaphopoden, Cephalopoden und Conodonten (Browne, I. 1959)
vergesellschaftet, also eindeutig als marin gekennzeichnet. Im Vergleich dazu ist
die Invertebratenfauna, die zusammen mit Dialipina und Orvikuina sp. gefunden
worden ist, sparlicher. Mit Dialipina (NW-Kanada) zusammen finden sich Ostra-
coden, Conchostraken (Estheria- und Leaia-ahnliche) , Brachiopoden (Lingula) und
Conodonten, mit Orvikuina sp. (Spitzbergen) zusammen Ostracoden und Lamel-
libranchiaten. Beide Sedimente enthalten aber auch Pflanzenreste (z.B. Trochiliscus
sowohl in den kanadischen als auch in den Grey Hoek Schichten) und so mogen beide
Sedimente als kiistennahe Bildungen angesehen werden, wie es P. F. Friend 1961
(S. 103) fiir die Grey Hoek Schichten annimmt.
Besonders auffallig an dem Vertebratenmaterial aus den Grey Hoek Schichten ist
die Vergesellschaftung der Palaeoniscoidea mit Thelodontierschuppen und zwar
den trompetenformigen, wie sie T. 0rvig 1957^ (Abb 2, 3) aus dem siidlichen Teil
Spitzbergens beschrieben hat. Auch in den Essigsaurelosungen des Gesteins dieser
Lokalitat (R0ykensata, Stormbukta, Sorkapp Land, Siidspitzbergen) fand sich ein
Palaeoniscoidea- Rest (PMO: A 34000). Die trompetenformigen Thelodontierschup-
pen treten auch zusammen mit dem Holotyp von Homostius arcticus Heintz (Heintz,
A. 1933, Taf. 9, Fig. i) auf, sind aber auBerhalb Spitzbergens unbekannt.
Eine weitere Faunenkomponente der Grey Hoek Schichten sind Poyo/^'s-ahnliche
Schuppen, die E. Jarvik 1950 (Abb. 326) und T. 0rvig 19570 (Abb. 8C) abgebildet
haben. Schuppen mit denselben charakteristischen Merkmalen sind auch von
anderen Lokalitaten in Spitzbergen, z.B. Jacobsdalen (0rvig, T. 19570, Abb. 8A, B),
und aus dem Polnischen Mittelgebirge bekannt (Kulczycki, J. 1961, Taf. 6, Fig.
1-8). Der Quarzit, in dem die Poro/^'s-ahnlichen Schuppen im siidlichen Teil des
Polnischen Mittelgebirges auf treten, wird ins Emsium eingestuft. Der gleiche
Schuppentyp ist ebenfalls mit Dialipina vergesellschaftet. Sofern die strati-
graphische Einstufung der Sedimente der drei Lokalitaten zutrifft — sie ist fiir alle
drei Ablagerungen unsicher — miiBte man eine stratigraphisch weite Verbreitung
dieser Poyo/^'s-ahnlichen Schuppen vom Unterdevon bis ins Mitteldevon anneh-
men.
Gemeinsam haben die Faunen von Spitzbergen und Australien Arthrodiren und
Acanthodier, beide Faunenkomponenten fehlen im kanadischen Material, treten
aber zusammen mit Orvikuina vardiaensis im Baltikum auf. Dagegen sind aus den
Grey Hoek Schichten in Spitzbergen keine Dipnoer bekannt, die sowohl in den
366 PAL^ONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON
australischen (Hills, E. S. 1958), den kanadischen (Jarvik, E. 1967) als auch den
baltischen Ablagerungen (Gross, W. 1942) auftreten.
Die Vertebratenfauna vom Murrumbidgee River (Australien) ist reichhaltiger als
die der beiden anderen Fundpunkte, so findet man in den Riickstanden der Essig-
saurepraparation Reste von Onychodus, Ohiolepis und Ohioaspis, Formen, die in
Schichten aus dem Unter-Mitteldevon Grenzbereich der verschiedensten Fund-
punkte auftreten: Bonebeds in Ohio, Indiana and Kentucky (Wells, J. W. 1944,
oberstes Unterdevon und unterstes Mitteldevon), Onondaga Kalk von Clifton Springs,
New York (oberstes Unterdevon mitO/wofls^'s^Heisdorfer Schichten bei Wetteldorf
im Rheinischen Schiefergebirge (oberstes Unterdevon mit Ohiolepis}1. Aus diesem
Vergleich heraus erscheint auch die Einstufung der Schichten am Murrumbidgee
River ins oberste Unterdevon durch die Vertebratenfauna bestatigt.
V. SUMMARY
Palaeoniscoid scales are described from Lower Devonian rocks of Southeastern
Australia and Northwestern Canada, and from Middle Devonian rocks of Spitsbergen.
The scales from Spitsbergen (the Grey Hoek beds, probably Middle Devonian) are
very similar in shape and histological structure to the scales of Orvikuina vardiaensis
Gross from the Middle Devonian of the Baltic region. The composition of the un-
divided surface of the ganoin is demonstrated and the growth of single stripes of
dentine -J- ganoin is shown. Because 79% of the scales are elongated, it is supposed
that elongated scales of the ventral region extended far up on the flanks in Orvikuina.
The peg on the dorsal border of the scales is absent.
New genera and species are erected for the scales from Lower Devonian rocks of
Northwestern Canada and Southeastern Australia, because the scales show characters
unknown in scales of other palaeoniscoid species. Dialipina salgueiroensis n.g. n.
sp. from Northwestern Canada has scales with separate ridges of dentine -f- ganoin.
The ridges end near the caudal border of the scales and the new dentine -f- ganoin
complex is deposited as isolated spots occupying positions between the ridges and
also between the spots in front of them.
Ligulalepis toombsi n.g. n. sp. from New South Wales, Australia, has deep scales
with a prominent antero-dorsal process. On the inner surface of the scales two
ridges are present. The first ridge near the rostral border of the scale is identical
with the ridge on rhombic scales which is penetrated by Sharpey's fibres. On the
caudal border of the second " ridge " the canal system of the dentine ends, and the
canals open caudally. In rostro-caudal section the scales show a shape comparable
only with a rostro-caudal section of a Cheirolepis scale, but the differences in
morphology and histology between them render improbable a close phylogenetic
relationship between Ligulalepis and Cheirolepis.
The scales of Orvikuina, Dialipina and Ligulalepis have thin, single-layered ganoin,
which is apparently a primitive character of palaeoniscoid scales. Cells are absent
1 Material im Besitz von Dr. T. 0rvig, Naturhistoriska Riksmuseet, Paleozoologiska sektionen,
Stockholm.
PAL^ONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON 367
in the bone of the scales of Dialipina and Orvikuina, but irregular canals of William-
son are present in both forms. These are non- vascular canals of Williamson (accord-
ing to the definition of T. 0rvig 1951, p. 365), each with an odontoblast-like cell in
the end on the inner surface of the scale. The processes given off along the canals
probably cannot be interpreted as processes of bone cells placed in the canals, because
the canal lumen is much smaller than the volume of lacunae containing bone cells.
If this is so, the concentration of bone cells around canals in the scales of Scanilepis
probably cannot be interpreted as a stage in the evolution of acellular bone tissue
like that of Dialipina and Orvikuina (cf. 0rvig, T. 19576, p. 487). Rather, the canals
with the concentration of bone cells in Scanilepis would seem to belong to the canal
system of the dentine, being ascending canals from the inner surface of the scales.
Similar canals are present in the scales of Orvikuina and Dialipina, and in these
forms they are clearly distinguishable from canals of Williamson. The canals in the
scales of Scanilepis are in other ways much like the canals in the scales of the recent
Polypterus (Aldinger, H. 1937, p. 227/228) and there is the same concentration of bone
cells around the canals.
The scales of Dialipina salgueiroensis, Ligulalepis toombsi and Orvikuina sp. were
found in marine beds. Together with Orvikuina sp., occur horn-like thelodontid
scales (known only from the Devonian of Spitsbergen) and Porolepis-like scales.
The Porolepis-like scales are associated also with the scales of Dialipina salgueiroen-
sis. Together with Ligulalepis toombsi occur fragmentary remains of other verte-
brates (Ohiolepis, Ohioaspis, Onychodus etc.). The fauna as a whole is comparable
with the " micro- vertebrates " of other localities from the upper Lower Devonian.
VI. ZITIERTE LITERATUR
ALDINGER, H. 1937. Permische Ganoidfische aus Ostgronland. Medd. Gr0nland 102, Nr. 3,
392 S., 105 Abb., 44 Taf., Kobenhavn.
BROWNE, I. A. 1959. Stratigraphy and structure of the Devonian rocks of the Taemas and
Cavan areas, Murrumbidgee river, south of Yass, N.S.W. /. Proc. Roy. Soc. N.S.W. 92,
S. 115-128, 4 Taf., Sydney.
CAVENDER, T. M. 1963. On the scale histology of Palaeoniscoid fishes. Diss. 86 S., 18 Taf.,
Chicago.
CURREY, J. D. 1961. The histology of the scales of Orvikuina (Palaeoniscoidea) . Palaont. Z.
35, H. 3/4, S. 187-190, 2 Abb., Stuttgart.
FOYN, S. u. HEINTZ, A. 1943. The Downtonian and Devonian vertebrates of Spitsbergen.
VIII. The English-Norwegian-Swedish Expedition 1939. Geological results. Norges
Svalb. u. Ishavs Unders., Skr. Nr. 85, 51 S., 18 Abb., 3 Taf., Oslo.
FRIEND, P. F., 1961. The Devonian stratigraphy of North and Central Vestspitsbergen. Proc.
Yorks. Geol. Soc. 33, Teil i, Nr. 5, S. 77-118, 5 Abb., Taf. 6, Hull.
FRIEND, P. F., HEINTZ, N. u. MOODY-STUART, M. 1966. New unit terms for the Devonian of
Spitsbergen and a new stratigraphical scheme for the Wood Bay Formation. Norsk
Polarinst. Arbok 1965, S. 59-64, i Abb., Oslo.
GOODRICH, E. S. 1907. On the scales of fishes, living and extinct, and their importance in
classification. Proc. Zool. Soc. London, S. 751-774. Abb- i97-204. 4 Taf-. London.
GROSS, W. 1942. Die Fischfaunen des baltischen Devons und ihre biostratigraphische
Bedeutung. Korrespondenzbl. Naturf.-Ver. zu Riga 64, Posen.
1953. Devonische Palaeonisciden-Reste in Mittel- und Osteuropa. Palaont. Z. 27, H.
1/2, S. 85-112, 13 Abb., 4 Taf., Stuttgart.
368 PAL^ONISCOIDEA-SCHUPPEN AUS DEM UNTERDEVON
HEINTZ, A. 1933. Revision of the Estonian Arthrodira. Arch. Naturkde. Estlands, I. Ser.
10, 4. Liefg., 115 S., 51 Abb., 23 Taf., Tartu.
HILLS, E. S. 1958. A brief Review of Australian Fossil Vertebrates, in: Studies on Fossil
Vertebrates (Watson-Festband) . S. 86-107; ed- Westell, T.St., Athlone Press, London.
JARVIK, E. 1950. Middle Devonian Vertebrates from Canning Land and Wegeners Halvo
(East Greenland). Part II. Crossopterygii. Medd. Gronland 96, Nr. 4, 132 S., 37 Abb.,
24 Taf., K0benhavn.
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GEOL. 1 6, 7. 34
TAP. i
FIGS. 1-8. Ligulalepis toombsi n.g. n.sp., Unterdevon, New South Wales, Australien.
FIG. i. BM: P. 48853. Spirifer yassensis Kalk, " right bank of Murrumbidgee, boulders
probably nearly in situ, on shore and up hillside, 2500 yds. due E. of Majurgong T.S. " Hohe
Schuppe aus der Region dicht hinter dem Schultergiirtel, rechte Korperseite. a. AuBenseite.
b. Innenseite. x 20.
FIG. 2. BM: P 48851. Spirifer yassensis Kalk, Lokalitat wie P. 48853 (= Fig. i). Hohe
Schuppe mit Griibchenorgan aus der dorsalen Region dicht hinter dem Schultergiirtel, linke
Korperseite. a. AuBenseite. b. Innenseite. x 20.
FIG. 3. BM: P 48857. Spirifer yassensis Kalk, " left bank of Murrumbidgee, boulders on
shore and hillside above, 1300 yds at 29° magnetic from Majurgong T.S. " Bruchstiick einer
hohen Schuppe der rechten Korperseite aus der vorderen Korperhalfte, AuBenseite. x 20.
FIG. 4. BM: P 48864. Holotyp. Spirifer yassensis Kalk (unterer Teil), Lokalitat wie
P 48853 (= Fig. i). Hohe Schuppe aus der vorderen Korperhalfte der linken Korperseite.
a. AuBenseite. b. Innenseite. x 20.
FIG. 5. BM: P 48854. ? Spirifer yassensis Kalk, " left bank of Murrumbidgee, base of steep
low cliff 1300 yds at 27° magnetic from Majurgong T.S. " Schuppe der rechten Korperseite
aus der vorderen Korperhalfte, AuBenseite. x 20.
FIG. 6. BM: P 48858. Spirifer yassensis Kalk, Lokalitat wie P 48857 (= Fig. 3). Schuppe
der rechten Korperseite wohl aus der Korpermitte. a. AuBenseite. b. Innenseite. x 20.
FIG. 7. BM : P 48860. Spirifer yassensis Kalk (nahe der Basis), " left bank of Murrumbidgee,
rock face in gully 1200 yds at 39° magnetic from Majurgong T.S. " Bruchstiick einer hohen
Schuppe, Blick auf die Hinterkante des zweiten " Kiels " mit Ofmungen des Kanalsystems
(= 6), links Innenseite, rechts AuBenseite der Schuppe. x 20.
FIG. 8. BM: P 48849. Bloomfield Kalk, " not in situ, on hillside south of inlet, 2750 yds
at 4° magnetic from Majurgong T.S. " Seitenlinienschuppe der linken Korperseite aus der
hinteren Korperhalfte. a. AuBenseite. b. Innenseite. x 20.
FIG. 9. Dialipina salgueiroensis n.g. n. sp., Unterdevon, PDelorme Formation, Anderson
River, gerade stromaufwarts des Zusammenflusses mit dem Ross River (68° n' Nord/i25° 49'
West), Nordwestkanada. NMC 11617. Schuppe der linken Korperseite aus der vorderen
Korperhalfte, AuBenseite. x 20.
FIG. 10. Cheirolepis canadensis (Whiteaves), Oberdevon, Scaumenac Bay, Kanada, Sto: S
927. Rostral-caudaler Vertikalschnitt ungefahr parallel zur Seitenlinie. x 100.
Bull Br. Mus. nat. Hist. (Geol.) 16, 7
PLATE i
34§
TAP. 2
FIGS. 1-4. Dialipina salgueiroensis n.g. n. sp., Unterdevon, PDelorme Formation, Anderson
River, gerade stromaufwarts des Zusammenflusses mit dem Ross River (68° n' Nord/i25° 49'
West), Nordwestkanada.
FIG. i. NMC 11609, Schuppe der rechten Korperseite, vermutlich eine Analschuppe,
AuBenseite. x 20.
FIG. 2. NMC 11608, Holotyp. Schuppe der linken Korperseite aus der vorderen Korper-
halfte. a. AuBenseite. b. Innenseite. x 20.
FIG. 3. NMC 11611. Schuppe der rechten Korperseite, vermutlich aus der Korpermitte
(= Abb. u), AuBenseite. x 20.
FIG. 4. NMC 11616, Teil des Schultergurtels (PCleithrum). a. AuBenseite. b. Innenseite.
Bull BY. Mus. nat. Hist. (Geol.) 16, 7
PLATE 2
1mm
TAP. 3
FIGS. 1-9. Orvikuina sp., Grey Hoek Schichten, unteres Mitteldevon, Westteil der Nordseite
von V-Vaerdalen, Wood Bay, Spitzbergen.
FIG. i. Sto: P 6403. Schuppe der linken Korperseite vermutlich von der Korperflanke.
a AuBenseite. b. Innenseite. x 27.
FIGS. 2-6. Schuppen aus der Ventralregion.
FIG. 2. Sto: P 6406. Schuppe der linken Korperseite. a. AuBenseite. b. Innenseite.
FIG. 3. Sto: P. 6400. Schuppe der linken Korperseite, AuBenseite. x 27.
FIG. 4. Sto: P 6401. Schuppe der rechten Korperseite. a. AuBenseite. b. Innenseite.
X27-
FIG. 5. Sto :P 6405. Schuppe der linken Korperseite. AuBenseite. x 27.
FIG. 6. Sto :P 6402. Schuppe der linken Korperseite. AuBenseite. x 27.
FIGS. 7, 8. Schuppen der rechten Korperseite aus der vorderen Korperhalfte mit schmalen,
stark verzierten Skulpturrippen.
FIG. 7. Sto :P 6408. a. AuBenseite. b. Innenseite. x 27.
FIG. 8. Sto :P 6414. AuBenseite. x 27.
FIG. 9. Sto: P 6407. GroBschuppe der linken Korperseite mit schmalen, stark verzierten
Skulpturrippen. AuBenseite. x 27.
Bull Br. Mus. nat. Hist. (Geol.) 16, 7
PLATE 3
1mm
TAP. 4
FIG. i. Ligulalepis toombsi n.g. n. sp., Spirifer yassensis Kalk, Unterdevon, " top of spur
falling west to left bank of Murrumbidgee, 1800 yds at 347° magnetic from Majurgong T.S. "
New South Wales, Australien. BM: P 48855. Hohe Schuppe der rechten Korperseite etwa
aus der Korpermitte, Durchlichtaufnahme in Wasser. X45-
FIG. 2. Polypterus bichir Geoffr. BM: P 48829 (Schliff von E. S. Goodrich), Vertikalschliff,
Ausschnitt aus der Knochenschicht. x 150.
FIG. 3. Scanilepis dubia (Woodward), Rhat, Bjuv, Skane, Siidschweden. Sto: S 1212.
Horizontalschliff, Ausschnitt, Knochenzellen um Williamson'schen Kanal. x 200.
FIG. 4. Orvikuina sp., Grey Hoek Schichten, unteres Mitteldevon, Westteil der Nordseite
von V-Vaerdalen, Wood Bay, Spitzbergen. Sto: S 2137. Dorsal-ventraler Vertikalschliff.
X75-
FIGS. 5-7. Dialipina salgueiroensis n.g. n. sp., Unterdevon, PDelorme Formation, Anderson
River, gerade stromaufwarts des Zusammenflusses mit dem Ross River (68° n' Nord/i25° 49'
West), Nordwestkanada.
FIG. 5. NMC 11605. Dorsal-ventraler Vertikalschliff durch den Kiel. X75-
FIG. 6. NMC 11607. Rostral-caudaler Vertilakschliff. X75-
FIG. 7. NMC 11604. Rostral-caudaler Vertikalschliff. X75.
Bull Br. Mus. nat. Hist. (Geol.) 16, 7
PLATE 4
• '•' :~a^-fe^sss^
: •* --'l^fcCr*;:: -?>3
> .
<i«— "^.'V*
'•^-
".^*Tj
! • x . >- , r^Av.
INDEX TO VOLUME XVI
New taxonomic names and the page numbers of the principal references are printed in Bold type.
An asterisk (*) denotes a figure.
A canthocrania 3, 6, 7, 8-9
laevis 3, 7, 8 ; PI. i, figs. 10-14
Acanthodii 353
Acipenser 209-210, 220-221, 329
ADAMS, C. G. 73-95
Aegiromeninae 173
Aetheretmon 351, 356
valentiacum 351
whitei 356
Agnatha 299, 302, 306, 329-330
Ahtiella 128-129, 135, 138, 140-141, 166, 167-169
concava 128-129, 135, 138, 141, 167, 168-169;
PI. 7, figs. 12-22
lirata 168
quadrata 128-129, 138, 140, 166, 167-169;
PI. 8, figs. 1-9
sp. 138
Ahtiellinae 166
Albula 226
Alepocephalus 227-229, 237
ro stratus 227*
Allothrissops 217, 223, 228-230, 232, 234, 237
Alveolinella 79
Amaroucium 308—309
constellatum 308*, 309
Amia 220, 329
Amphilichas 129, 132, 139, 141-142, 194, 195
hibernicus 195
sp.l. 129, 139, 194, 195; PI. 14, figs. 10, 14-15,
17
sp.2. 129, 132, 139, 141, 195 ; PI. 14, figs.iS-ig
Amphioxus 145, 285, 300, 303, 314, 328-330,
333-334
Amphistegina 78
Ampyx 129-130, 132, 139, 141, 185, 186, 187
domatus 185
linleyensis 187
nasutus 132
salteri 187
sp.l. 129, 139, 185, 186 ; PI. 13, fig. 8
sp.2. 129, 139, 141, 186, 187 ; PI. 13, figs. 7,
10-12
sp. 185
Anglesey 9
Faunal affinities 140-142
lists 138-140
Key to localities 131
Stratigraphy 130-132, 133, 134-142
Angusticardinia 140, 160
Angusticardiniidae 128, 160
Anomalocystites incipiens 277
Anomia craniolaris 4
Anomites resupinatus 10
Anoplia 48
Anopliinae 48
Anopliopsis 48
Antedon 260
Antigonambonites 128, 134, 138, 140, 163, 164
costatus 164
pyramidalis 128, 134, 138, 140, 163, 164 ; PI.
6, figs. 12-18
sp. 138, 140
Apatorthis 160
Apomatella 128, 135, 138, 163
sp. 128, 135, 138, 163 ; PI. 6, figs. 8-1 1
Archaeorthis 157
Archaias asmaricus 83
Arctophyton gracile 358
Argentina 226, 230, 237
Aristoharpes 184
Articulata 10
Asaphidae 128, 179
Asaphina 195
Asmari limestone 75-76
Atelelasmatinae 163
A thabaskiella
Australosomus 208, 220
Austrotrillina 73-79, 80, 81, 82, 83-95
asmariensis 73, 76-77, 81*, 82, 84-85, 88-
95 ; PI. i, figs. 1-12
brunni 73, 85, 86, 89, 93-94 ; PI. 6, figs. 6, 8
howchini 73, 78-80, 81*, 82, 84-85, 86, 87-95 ;
PI. 2, figs. 1-6 ; PI. 5, figs. 4-5, lo-ii ; PI. 6,
figs. 5, 7
paucialveolata 73, 78, 82, 84, 89, 90-91, 93~95 ;
PI. 3, figs. 1-6
range 74
sp.n. 80
sp. PI. 5, figs, i, 6-8
striata 73, 79-80, 81*, 82, 84-86, 88-91, 92,
INDEX
93-95 J PI- 3. figs- 7-8 : PI- 4> figs. I~I3 :
PI. 5, figs. 2-3,9; PL 6, fig. 9
striata/howchini PL 3, fig. 9
BATES, D. E. B. 127-197
Bathyuriscus 196
Bergamia 129, 135, 239, 184, 185
rhodesi 185
8p. 129, 135, 139, 184, 185 ; PL 13, figs. 3-4, 9,
13
Bikini 79
Bilobia 128, 137-138, 141, 171, 172
musca 128, 137-138, 141, 171, 172 ; PL 9, figs.
10-13
Birgeria 221, 231-232
Borelis 77, 80, 83
melo curdica 76
Pygmaea 77
pygmaeus 77, 80
Boreosomus 210
Brochocarina 3, 31, 32, 33*, 34-38, 46
wexfordensis 3, 34, 35-36, 37*, 38, 46 ; PL 4,
figs. 24-26 ; PL 5, figs. 1-23
BRUNTON, C. M. C. 3-68
Calcichordata 244, 246-247, 277, 323, 327, 330,
333-334. 336
Callichthys 363-364
Calymene 193
parvifrons 193
tristani 193
Calymenid 129, 139, 192, 193 ; PL 14, figs. 8-9,
12-13
Calymenidae 129-130, 192
Calymeninae 192, 193
Camarella balcletchiensis 178
Camerella 128, 136, 138, 142, 178
sp. 128, 136, 138, 178 ; PL ii, figs. 7, 9-11
unicostata 178
Camerellidae 128, 178
Camerellinae 178
Carpoidea 245
Catenipora sp. 353
Cephalaspidae 331
Cephalochordata 244, 247, 328, 332-333
Ceratocystis 246, 258-259, 271, 323-325
perneri 246, 258-259, 271, 324-325
Ceraurinella 129, 140, 142, 187, 188-189
sp. 129, 140 187, 188-189 ; PL 13, figs. 14-22
Ceraurus 188
Chapmanina 76—77
Charophyta 353
Cheirolepis 345, 351, 363, 366
Cheiruridae 129, 187
Cheirurinae 187
Chinianocarpos 246, 282, 288-289, 291, 295, 307,
314, 323-325. 329-331, 333
thorali 246, 282, 288-289, 291, 295, 307, 314,
323-325, 329-330, 333
Chonetacea 3, 46, 47, 48, 66
Chonetes 50
buchianus 67
laguessiana 66
minuta 50
subminima 50
Chonetidae 3, 48
Internal morphology 58*
Chonetina 48
Chordata 244-245, 247, 277, 327, 330, 333
Christmas Island 80
Cincta 245
Cladoselachiidae 353
Clavelina rissoana 288*
Claxby Beds 103-105
Climacograptus 132, 135
antiquus 132
scharenbergi 132, 135
sp. 132, 135
Clinambon 162
Clitambonitacea 128, 161
Clitambonites 128, 137-138, 141, 162
sp. 137-138, 141, 162 ; PL 6, fig. 4
Clitambonitidae 128, 162
Clitambonitidina 128, 161, 165
Superfam. & genus unknown 128, 165, 166 ;
PL 7, figs. 5, lo-n
Clitambonitinae 162
Clupavus 226, 229-230
Clupea 208, 218, 228
Clupeomorpha 229, 234, 237
Coccolepis 231-232
Conchostraca 353, 365
Conodonta 353, 365
Corboveles 231
Coregonus 230, 237
Cornuta 244-245, 247, 333, 336
Corynexochida 140, 195
Cothurnocystidae 247
Cothurnocystis 243-244, 246, 247, 248-264, 265,
266-277, 282-283, 287-288, 291, 314, 317,
323-326, 333-336
americana 258-259, 324
curvata 243-244, 246, 253, 259, 262, 265, 266,
267*, 268*, 269*, 270*, 271, 272*, 273*, 274*,
275*. 282, 287, 291, 314, 323, 325, 333-336 ;
PL 3, figs. 2-10 ; PL 4, figs. 1-7
elizae 243-244, 246, 247, 248, 249*. 250*, 251*,
252*, 253, 254*, 255, 256*, 257-260, 261*.
262-266, 271, 273, 275-277, 282-283,
287-288, 317, 323-326, 333-336 ; PL i, figs.
i-io ; PL 2, figs. 1-9 ; PL 3, fig. i
primaeva 324
Crania 3, 4, 5, 6-9
anomala 5
dodgei 5
kirkbyi 5, 7
laevis 7
quadrata 3,5, 6-7
spiculata 7
Craniacea 3, 4
INDEX
371
Craniata 244, 247, 333
Craniella quadrata 5
Craniidae 3, 4
Craniidina 4
Crinoid stem section 259*
Crinozoa 327-328
Cryptolithinae 184
Cyathaspididae 301-302, 307-308, 329, 336
Cyclomyonia 157
Cyclopyge sp. 135
Cyclothyridinae 101, 108
Cyrtonotella 127, 136-138, 141-142, 145, 146
kukersiana 145
sp.l. 127, 137-138, 145 ; PI. 2, figs. 9-10, 13
sp.2. 127, 136, 139, 146 ; PI. 2, figs. 14-16
sp. 141-142
Dactylogonia sp. 128, 135, 139, 175 ; PI. 10, figs.
7-8
Dalejina 19
Dalmanella 127, 136, 139, 155, 157, 158
sp. 127, 136, 139, 158 ; PI. 5, figs, lo-n
testudinaria 155
Dalmanellidae 127, 158
Dasyalosia 4
lamnula 4
panicula 4
Davidsoniacea 3, 31
Derbyia ambigua 34-35
Derbyiinae 32, 46
Derbyoides 32, 33*, 34, 36
nebrascensis 36
Derbyoidinae 31
Dialipina 343, 351, 352, 353-357. 363-367
salgueiroensis 343, 352, 353, 354,* 355*. 356,
357*. 366-367 ; PI. i, fig. 9 ; PI. 2
Dichometopsis 196
Dictyonema 135
Didymograptus 130, 132, 134-135
artus 135
bifidus 132, 134-135
extensus 130, 134
hirundo 135
murchisoni 134-135
stabilis 135
Digitata 245
Dinorthis 127, 137, 139, 141, 144, 154
flabellum 155
sp. 127, 137, 139, 141, 154
Diparelasma 157
Dipnoi 353
Dolerorthidae 127, 152
Dolerorthinae 152
Dolerorthis 127, 137, 139, 141, 152
sp. 137
tenuicostata 127, 137, 139, 141, 152 ; PI. 4, figs.
4.6-7
Dolichometopidae, 195
Dorypterus 231
Echinodermata 244, 327, 330, 333
Echinosphaerites sp. 132, 137
Elopomorpha 229, 234, 237
Elops 215, 219, 226, 229-230, 232, 237
Enchelion 219
Eniwetok 79
Enteletacea 3, 10, 127, 157, 160
Enteletidae 3, 10
Eobronteus 181
curtus 181
reedi 181
Eochonetes advena 47
Eohomalonotinae 193
Eomarginifera (Eomarginiferina) trispina 4
Eoplectodonta 128, 137, 139, 141, 172
lenis 128, 137, 139, 141, 172 ; PI. 9, figs. 14-18
Equirostra 177
Estheria 365
Estlandia 128, 138-139, 164, 165
sp. 128, 138-139, 164, 165 ; PI. 7, figs. 2-4, 6-9
Eulepidina 76, 78, 80, 83
dilatata 80
Eurycormus 217
Eusthenopteron 301
Favosites 353
Finkelnburgiidae 157
Flexicalymene 193
Flosculinella 79-80, 87-88
bontangensis 80, 87—88
Fulletby Beds 103, 105-108
Gillicus 224, 226
Globosochonetes 3, 48, 49, 50-53, 59
parseptus 3, 48, 49, 50-51, 52*, 53 ; PI. 7,
figs. 8-27
Glossograptus hincksii fimbriatus 135
Glossopleura 195-196
Glyptambonites 171
Glyptograptus teretiusculus 137
Glyptorthinae 152
Gogia 259
Gonambonitacea 128, 163
Gonambonitidae 128, 163, 164
Gonambonitinae 163
Gonatodus brainerdi 363
Gravicalymene 193
Haly sites 353
Haplolepis tuberculata 351
Harknessella 127, 139, 159
sp. 127, 139, 159 ; PI. 5, fig. 16
Harknessellidae 127, 159
Harpes 142
Harpidae 129, 183
Hebertella vespertilio 144
Hemichordata 327-328
Hesperonomia 140, 143
louisensis 143
Hesperonomiella 127, 129, 134, 138-140, 142, 143
372
INDEX
carmelensis 127, 129, 134, 139-140, 142, 143 ;
PI. i, figs. 1-6
sp. 134, 138
Hesperonomiidae 127, 142, 143-144
Heterolepidotus sp. 363, 365
Hiodon 224-226, 228-229, 234, 236-237
alosoides 224, 225*, 226
Hipparionyx 32, 34
Homalonotidae 129, 193
Homostius arcticus 365
Horderleyella 127, 137, 139, 141, 159
sp. 127, 137, 139, 141, 159 ; PI. 5, fig. 15
Huenellidae 128, 176
Ichthyodectes 224, 226
Illaenidae 129, 181
Illaeninae 181
Illaenus 129, 136, 140, 142, 180, 181, 182
caecus 180-182
linnarssoni 183
revaliensis 182
sp. 129, 136, 140, 181, 182 ; PI. 12, figs. 8-13,
15
Ilmarinia 128, 137, 139, 141, 162
sp. 128, 137, 139, 141, 162 ; PI. 6, figs. 6-7
Inarticulata 4
Inversella 138, 140, 169-170
angulata 169
borealis 169
perundosa 169-170
sp. 138
Isorhynchus 177
JEFFERIES, R. P. S. 243-336
Jenkinsia 226
Kiaeromena 128, 136, 139, 142, 175, 176
sp. 128, 136, 139, 142, 175, 176 ; PI. 10, figs. 9-
10
Kirimalai limestone 78-79
Kirkuk 76, 78
Krotovia lamellosa 4
Kullervo 128, 137, 139, 141, 165
panderi 128, 137, 139, 141, 165 ; PI. 6, figs.
19-22 ; PI. 7, fig. i
Kullervoidae 128, 165
Lagynocystidae 323, 328-330
Lagynocystis pyramidalis 246, 254
Lambeioceras Iambi 353
Lamellaerhynchia 101, 108, 109-117, 211
gillieroni 117
hauteriviensis 116
julenia 101, 116, 117 ; PI. 3, figs. 6-7
multiformis 109
picteti 101, 117 ; PI. 3, figs. 8-9
rawsoni 101, 116 ; PI. 4, figs. 11-15
rostriformis 101, 108, 109, no*, in, 112*, 113,
116-117, 121 ; PI. i, figs. 1-6 ; PI. 2, figs. 1-9 ;
PI. 3, fig. 2
walkeri 101, 113, 114, 115*, 116 ; PI. 4,'figs. 3-8
claxbyensis 1 13, 114, 115-116 ; PI. 3, figs. 3-4
Leaia 365
Lenorthis 127, 134-135, 138-140, 146, 147, 148
alata 140
proava 127, 134, 138-140, 146, 147-148 ; PI. i,
fig. 21 ; PI. 2, figs. 1-8
sp. 127, 135, 138, 148 ; PI. 2, figs. ii-i2
Lepidocyclina 76-78, 80, 84-85, 91
dilatata 80
sp. 85, 91
tournoueri 80
Lepisosteus 233, 329
Leptaena 21-23, 26-27, 29> 32> 34~35, 5°. I28,
137, 139, 141, 169, 174
analoga 22, 26, 29
crenistria 34-35
depressa 22-23, 26
distorta 22—23, 26, 30
rhomboidalis 22, 26, 169
rugosa 22
sp. 128, 137, 139, 141, 174 ; PI. 10, figs. 3-6
subminima 50
transversalis 22
Leptaenella 21, 23
Leptaenidae 3, 21, 128, 174
Leptaeninae 21
Leptagonia 3, 21, 22—31
analoga 3, 22-23, 24*. 25*> 26, 27*, 28*, 29,
30*, 31 ; PI. 3, figs. 26-31 ; PI. 4, figs. 1-9
Leptellinidae 128, 171
Leptestiidae 128, 170
Leptestiina 128, 132, 137, 139, 141, 171
derfelensis 128, 132, 139, 141, 171 ; PI. 9, figs.
7-9
sp- 137
Leptestiinae 170
Leptestiininae 171
Leptolepis 204, 206, 215, 217, 219-220, 222-230,
232,234-237
coryphaenoides 204, 206, 215, 219-220, 222*,
223, 225, 228, 230, 235-236
dubia 204, 206, 215, 220, 223, 224*, 226-230,
234. 237
normandica 204, 206, 215, 217, 219, 222-223,
225, 228, 230
Lichas hibernicus 195
Lichidae 129, 194
Ligulalepis 343, 345, 347-351, 363, 365-367
toombsi 343, 345, 347*, 348, 349*, 350*, 351,
366-367 ; PI. i, figs. 1-8 ; PI. 4, fig. i
Limbimurina 169
Lingula 135, 365
Linoporellidae 128, 159
Lissocrania 4, 5
Ly copter a 218-219
Malta 80
Marginopora vertebralis 87
Matherella acuticostata 130, 134, 141
INDEX
373
Meandropsina anahensis 83
Meekellidae 3, 42
Meekellinae 42, 46
Megalops 226, 228
Melinau Limestone 79
Mesonomiinae 176
M etacamerella 128, 136, 139, 142, 178, 179
balcletchiensis 128, 136, 139, 178, 179 ; PI. n,
figs. 12-14
Metorthis 144
Miliolidae 80, 93
Miogypsina 78, 85, 88
globulina 85
irregularis 85
thecidaeformis 88
Miogypsinoides 80, 85, 88
complanatus 80, 85
dehaarti 88
Mitrata 244-245, 277, 329, 333, 336
Mitrocystella 243-247, 277, 278-311, 313-319,
321-325,333-336
barrandei 289, 293, 295-296, 305, 307, 310, 325,
335 ; PI. 6, figs. 2-3, 5
incipient 277, 293, 307 ; PI. 7, fig. 5 ; PI. 9,
figs- 3-4
miloni 243-244, 246-247, 277, 278*, 279*,
280*, 281*, 282-283, 284*, 285*, 286*,
287*, 288-289, 290*, 291*, 292*, 293-296,
297*, 298*. 299-311, 313-319, 321-323,
333-336 ; PI. 4. figs- 8-10 ; PI. 5, figs, i-n ;
PI. 6, figs, i, 4, 7, 10-12 ; PI. 7, figs. 1-3,
6 ; PI. 9, figs. 1-2 ; PI. 10, figs. 1-3
Mitrocystidae 277
Mitrocystitidae 277, 289, 307, 310, 314, 323,
328-331
Mitrocystites 244, 246-247, 257, 282, 295-296,
298, 3°5-3°7> 310, 3"-325, 333-336
mitra 244, 246-247, 257, 282, 295-296, 298,
305-307, 310, 311*, 312*, 313*, 314*, 315*.
316*, 317*, 318*, 319, 320*, 321*, 322-323,
325, 333-336 ; PI. 6, figs. 6, 8-9 ; PI. 7, fig.
4 ; PI. 8, figs, i-io ; PI. 9, figs. 5-6 ; PI. 10,
figs. 4-8
Monella 129, 134, 140, 195, 196-197
perplexa 129, 134, 140, 195, 196, 197 ; PI. n,
figs. 15-21
sp. 134
Monorthis 127, 129, 134, 138-139, 141, 144, 145
sp. 138
typis 127, 129, 134, 139, 141, 144, 145 ; PI. i,
figs. 7-13
Moythomasia 363
laevigata 363
nitida 363
Nanorthis 157
Nectaspis 302, 304
areolata 302*, 30*4*
Nemagraptus gracilis 132
Nematonotus 226, 230
Nephrolepidina tournoueri 80
Neseuretus 129-130, 134, 140, 193
monensis 129-130, 134, 140, 193 ; PI 14, figs.
ii, 16
Nicolella 127, 132, 137, 139, 141, 150, 151
humilis 127, 137, 139, 141, 150, 151 ; PI. 3,
figs- 5, 7-9
sp. 132
Notanoplia 48
Nothorthis 157
Nummulites fichteli 76, 78, 83-84, 91, 95
Ogygia 179, 195-196
selwyni 179
Ogygiocaridinae 179
Ogygiocaris 128, 134, 140, 179, 180
selwyni 128, 134, 140, 179, 180 ; PI. 12, figs.
1-2, 5-6
sp. 134
Ohioaspis 366—367
Ohiolepis 366—367
Omboniinae 42
Onniella 127, 137, 139, 141, 158
anelinei 158
sp. 127, 137, 139, 141, 158 ; PI. 5, figs. 12-14
Onychodus 366-367
Operculina 78
Orbicula quadrata 5
Orbiculata trigonalis 8
Orbiculina 79
malabarica 79
sp. 79
Orbulina 74, 85, 87-88
suturalis 87
universa 87-88
Order uncertain 128, 179 ; PI. 10, figs. 18-24
Orthambonites 127, 135-139, 141, 148, 149
sp.l. 127, 135, 139, 141, 148 ; PI. i, figs. 14,
16-17
sp.2. 127, 137, 139, 141, 148, 149 ; PI. i, figs.
15, 18-20
sp- 135-138
Orthacea 127, 142
Orthida 10, 142, 179
Orthidae 127, 145, 157
Orthidina 142
Orthinae 145
Orthis ii, 53, 140, 144, 146-148, 151, 155
bifurcatus 148
calligramma 146-147
proava 146
carausii 140, 146
divaricatus 148
hardrensis 53
parvicrassicostatus 149
proava 146, 148
resupinata ii
testudinaria 155
vespertilio 144
374
INDEX
Orthopleura 40
Orthotetes 32, 34-36
Orthotetidae 3, 31
Orthotetinae 31, 32, 39, 46
Orthotetinid gen. et sp. indet. 3, 39 ; PL 7, figs.
Orvikuina 343-345, 356, 357, 358-367
sp. 343, 357, 358, 359*. 360, 361*. 362* 363,
365, 367 ; PL 3 ; PL 4, fig. 4
vardiaensis 356, 360-362, 365-366
Osmerus 230, 237
Ostariophysi 229, 234, 237
Osteoglossomorpha 229, 234, 237
Osteostraci 331
Ostracoda 353, 365
OWEN, E. F. 101-121
Palaeoniscoidea 343, 345-346, 351, 353, 357-358,
363-365
Palaeostrophomena 128, 136—137, 139, 141—142,
170, 171
magnified 170-171
sp. 128, 136-137, 139, 141-142, 170, 171 ; PL 9,
figs. 1-2, 4-5
Panderina 127, 129, 134-135, 138-140, 151, 152
lamellosa 127, 129, 134-135, 138-140, 151,
152 ; PL 3, figs. 10-18
sp. 138
Parallelasmatidae 128, 178
Pata Limestone 79
PATTERSON, C. 203-237, 239
Paurorthidae 127, 157
Paurorthis 127, 135, 139, 157, 158
sp. 127, 135, 139, 157, 158 ; PL 5, figs. 6-9
Pecten maximus 323
Peltocystis cornuta 246, 289, 323
Pemba Island 78
Peneroplis 76, 80, 83
evolutus 76, 80, 83
thomasi 76, 83
Pentameracea 128, 178
Pentamerida 176
Perleidus stochiensis 363, 365
Petraia sp. 164
Petrocrania 5
Petromyzon 299, 303, 307-308
Philhedra 3, 5, 8, 9
baltica 8
trigonalis 3, 8, 9 ; PL i, figs. 15-29
Philhedrella 5, 9
Pholidolepis 203-204, 206, 208-212, 214-217,
219-222, 229-230, 233, 235, 236-237
dorsetensis 204, 209*, 211* ; PL 2 ; PL 3, fig. 2 ;
PL 5, fig- 2
Pholidophoridae 235, 236
Pholidophoroides 206
Pholidophoropsis 203-204, 206, 208-210, 212,
214-215, 217-222, 229-230, 235, 236-237
caudalis 206, 209, 215, 217, 218*
maculata 204, 206, 208-210, 212, 214*, 215,
217, 218*, 222 ; PL 4
Pholidophorus 203-210, 212, 217, 219-222, 233,
235, 236-237
bechei 203-204, 205*, 206, 207*, 208-210, 212,
213*, 214-215, 216*, 217-219, 222, 236-237 ;
PL i ; PL 3, fig. i ; PL 5, fig. i
Pholidopleuridae 218
Phyllocystis 246, 324-326
blayaci 246
crassimarginata 246
sp. 324
Placoparia 129, 135, 137, 140, 191, 192
barrandei 192
cambriensis 192
sp. 129, 135, 137, 140, 191, 192 ; PL 14, fig. 5
zippei 192
Placopariinae 191
Plaesiomyidae 127, 154
Plaesiomyinae 154
Plaesiomys 127, 136-137, 139, 154, 155
robusta 127, 136, 139, 154 ; PL 4, figs. 8-12
sp. 127, 136-137, 139, 154, 155 ; PL 4, figs.
13-15
Platycalymene 193
Platystrophia 127, 132, 136-137, 139, 141, 155
precedens 127, 132, 137, 155
major 127, 137, 139, 141 155 ; PL 4, figs.
17-18
sp. 136-137
Platystrophiinae 155
Plectambonitacea 128, 166
Plectambonitidae 128, 166
Plectodonta transversalis 22
Plectorthidae 127, 155
Plectorthinae 155
Plectorthis 127, 139, 155
sp. 127, 139, 155 ; PL 4, figs. 16, 19
Pleurorthis 127, 129, 134, 138-139, 141, 149, 150
costatus 127, 129, 134, 139, 141, 149, 150 ; PL
2, figs. 17-19 ; PL 3, figs. 1-4, 6
sp.i38
Plicatifera 22
Plicochonetes 3, 48, 50, 65, 67, 68
buchianus 3, 67, 68 ; PL 9, figs. 27-32
subminimus 50
Pliomera sp. 191
Pliomerella americana 191
Pliomeridae 129, 190
Pliomerinae 190
Pliomerops 129, 136, 140, 142, 190, 191
canadensis 191
sp. 129, 136, 140, 142, 190, 191 ; PL 14, figs.
3-4- 6-7
Polyodon 209-210, 220-221, 231-232
Polypterus 329, 363-365, 367
Polytoechiidae 128, 161, 166
Porambonitacea 128, 176
Porambonites 128, 134, 139-140, 177
altus 177
177
INDEX
375
planus 177
sp. 128, 134, 139-140, 177 ; PI. ii, figs. 1-6, 8
Porambonitidae 128, 177
Porolepiformes 353
Porolepis 363, 367
Praeorbulina cf. glomerosa 88
Praerhapydionina delicata 76, 80, 83
Producta analoga 22-23, 29
Productacea 3-4, 46-47, 50
Productidina 46
Productorthinae 150
Productorthis 151-152
Productus 22, 60
plicatilis 22
Protocanthopterygii 229, 234, 237
Protobronteus 129, 136, 140, 142, 180, 181
greenlyi 129, 136, 140, 142, 180, 181 ; PI. 12,
figs. 3-4, 7
reedi 181
Pseudoleptaena 21, 23, 26-27
distorta 27
Psilodendrion spinulosum 358
Pteronisculus 210, 220
Ptilograptus 130
Ptychoglyptinae 173
Ptychoglyptus 128, 136, 139, 142, 173
kindlei 173
sp. 128, 136, 139, 173 ; PI. 10, figs. 1-2
valdari 173
virginensis 173
Ptychopleurella 127, 135, 137, 139, 141, 152, 153
bouchardi 153
oklahomensis 153
sp.l. 127, 139, 141, 152, 153 ; PI. 3, figs. 19-23
sp.2. 127, 137, 139, 141, 153 ; PI. 4, figs. 1-3, 5
sp- 135
Rafinesquina llandeiloensis 142
Raphiophoridae 129, 185
Rectotrophia 128-129, 134, 139, 141, 176, 177
globularis 128-129, 134, 139, 141, 176, 177 ;
PL 10, figs. 11-17
Rectotrophiinae 176
Reinversella 128-129, 134, 138-140, 169, 170
monensis 128-129, 134, 139-140, 169, 170 ;
PI. 8, figs. 10-17
sp. 138
Rhadinichthys 351, 356
Rhipidomella 3, 17, 18-21, 59
henryhousensis 19
michelini 3, 17, 18, 19*, 20, 21 ; PI. 3, figs. 1-25
Rhipidomellidae 3, 17
Rhynchonella 101, 109, 112-113, H7, 118-121
depressa 109
loxia 118-120
multiformis 109, 112
parkhillensis 101, 117, 118*, 119 ; PI. 4, figs.
9-10
rouillieri 1 18-120 *
eltonica 119
speetonensis 101, 119, 120*, 121*, PI. 3, fig. 5 ;
PI. 4, figs. 1-2
walkeri 113-114
Rhynchonellacea 108
Rhynchonellidae 101, 103, 108
Rhynchorthis 128-129, 134, 138-140, 160, 161
rotundus 128-129, 134, 138-140, 160, 161 ;
PI. 5, figs. 19-26
Rhynchotrema 160
Rhysostrophia 179
Rotalia 85
Rugosochonetes 3, 53, 54-66, 68
celticus 54-56, 63, 66
delicatus 3, 62, 63, 64* ; PI. 9, figs. 3-15
hardrensis 54-55
hindi 63
silleesi 3, 55, 56, 57*, 58*, 59*, 60-64, 66 ;
PI. 8, figs. 10-27
transversalis 3, 65, 66 ; PI. 9, figs. 16-25
Rugosochonetid shell structure 57*
Rugosochonetinae 48, 53
Saipan, 79
Salmo 206, 218
Salopia 128, 137, 139, 141, 159
salteri gracilis 128, 137, 139, 141 159 ; PI. 5,
figs. 17-18
Salvelinus grayi 227, 229
Sarawak 79
Sardinioides attenuatus 230
Scanilepis 363-365, 367
dubia 363, 365
Schellwienella 3, 35, 42, 43-46
aspis 42-43
radialiformis 42
radialis 3, 42, 43, 44*. 45*, 46 ; PI. 6, figs. 13-24
Schizophoria 3, 10, 11-17, 47' 59
connivens 10
dorsosinuata 3, 10, 11, 12-13, X4*> I5~I7 >' PI- 2>
figs. 7-37
hudsoni 10
nuda 10, 15
resupinata 3, 10, 11, 12-17
elboltonensis 10
gigantea 10
la ta 10
pinguis 10
rotundata 10, 13
striatula 12, 15
sulcata 12
Schizophoriinae 10
Schuchertella 3, 34-35, 40, 43, 353
nevadensis 353
pseudoseptata 35
wexfordensis 31, 34-35
Schuchertellidae 3, 39
Schuchertellinae 39, 40, 46
Schuchertellopsis 40
SCHULTZE, H.-P. 343-367
Selenoharpes 129, 136, 140, 142, 183, 184
376
INDEX
sp. 129, 136, 140, 142, 183, 184 ; PI. 13, figs.
1-2 ; 5-6
youngi 184
Sericoidea 128, 132, 139, 141, 173, 174
abdita 128, 132, 139, 141, 173, 174 ; PI. 9, figs.
3,6
Serratocristata 3, 39, 40-41
fistulosa 3, 39, 40, 41 ; PI 6, figs. 1-12
Skenidiidae 127, 156
Skenidioides 127, 134-135, 138-139, 141, 156,
157. 164
sp.l. 127, 134, 139, 156, 157 ; PI. 5, figs. 1-2
sp.2. 127, 135, 139-141, 156, 157 ; PI. 5, figs.
3-5
sp. 138
Soluta 245
Sorites 79
Soudleyella avelinei 158
Sowerbyellidae 128, 172
Sowerbyellinae 172
Sphaerexochinae 189
Sphaerexochus 129, 132, 140, 189
bilobatus 189
sp. 129, 132, 140, 189 ; PI. 14, figs. 1-2
Spirifera 35, 42-43
crenistria 35, 42
radialis 42-43
Spiroclypeus 78-80, 87-88
blankenhorni ornata So
orbitoideus 79
pleurocentralis 79
tidoenganensis 88
Stegotrachelus finlayi 362-363
Stenopareia 129, 136, 140, 182, 183
camladica 183
linnarssoni 129, 182, 183 ; PI. 12, figs. 14, 16-23
sp. 136, 140
Strepheoschema fouldenensis 356
Streptorhynchinae 40, 46
Streptorhynchus 31, 34-35, 39, 41-43
crenistria 34-35, 39, 42-43
radialis 42-43
Stricklandinia balcletchiensis 178
Strophalosiacea 47
Strophomena 21-22, 29, 31, 34-35
crenistra 34-35
rhomboidalis 22, 29
analoga 29
Strophomenacea 3, 21, 128, 174
Strophomenida 21, 166
Strophomenidina 166
Sturgeons 232
Stylophora 244-245, 247, 259, 277, 323, 327-33°,
333, 336
Sycidium sp. 353
Synhomalonotus monensis 130, 193
Syntrophiidina 176
Taberina malabarica 79, 87-88
Tapajotia 32, 33*. 34-35
tapajotensis 35
Tarassius 221
Tarpon 226
Teleostei 203, 237, 364
definition 234-235
Terebratula 17, 108-112, 119
depressa 109
michelini 17
rostralina 108-109, 112
rostrata 109
rostriformis 108, no
varians 119
Tetragraptus headi 134
Tetralichinae 194
Thrissops 217, 223-224, 228-230, 232, 237
Thysanopeltidae 129, 180
THURRELL, R. G. 101-121
Tornquistia 48, 50
polita 50
Trillina howchini 80, 82, 86, 89
Trinucleidae 129, 184
Tritoechia 128, 134, 138-139, 141, 161, 162
sp. 128, 134, 138-139, 141, 161, 162 ; PI. 6,
figs. 1-3, 5
transversa 162
Trochiliscus 353, 365
sp- 353
Turseodus 219
Urochordata 244, 247, 333
Urocles 220
Werriea 32
Xiphactinus 224, 226
Xystostrophia umbraculum 41
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